There are overnight boats between France and Ireland - I took it once and they though not cruise ships are well-equipped large boats with lots of entertainment, etc.

Going by train or car? or plane to Ireland - Ryan Air would be a good bet I'd think but you may have to leave from Beauvais, an hour northwest of Paris perhaps.

I think a lot falls into your traveling style, budget, interests and for how long you can visit.
I think you 3rd option, a cruise, is advisable only if you are interested on the cruise experience, not to really get to know places...

I have only been in Paris with a side trip to Versailles and Poitiers on February a few years ago, so not a destination expert there, but judging by second hand information, a car might be necessary to explore the smaller towns that add significant value to a visit in Loire, Burgundy etc. Many people for some reason do not realize how cold and often rainy Paris can be, of course Paris is an all year around destination, but not sure if countryside is or is not suitable on March.
I am much more familiar with Ireland and have been multiple times in 3-4 weeks' long trips,mostly in winter months, more recently late February to end of March a few years ago. Again a car would give maximum flexibility as public transport is time consuming and does not always reach small places, but I believe that most destinations on your list are well connected on train and of course bus. March 17th, St Patrick's day, is traditionally a date around which many attractions that are closed on winter open for summer. I think I was in Killarney around the 10th-15th March a few years ago, and I attended the first guided tour of Ross Castle for the season, attraction was closed for winter. Dublin as every major city is "open" and vibrant all year around, ditto Galway, smaller/more touristy towns might feel somehow deserted. I remember sharing with an other girl an 8 persons dorm and maybe seen no more than 10 guests in a hostel I stayed in Killarney on early March... Hotels and hostels I have stayed in Galway and Dublin were much busier even on January...
Some smaller towns might feel somehow isolated so...Personally I am fine with that, I see it as an opportunity to see how "real" life is and to meet locals.
No one visits Ireland for weather, any time of the year you may experience the whole 4 seasons in a day.
Day light hours might be an issue at this time of the year as dark comes early and you can do less in a day!
Just some general observations : )))

The key factor is your timing---March.
I would stay south. Ireland will be cold and wet.
Think Sicily or Greece.

We spent a few days in Paris mid-March and we still needed to wear our winter jackets however were able to eat outside at lunch one day. Cafes will have heaters on so you can sit outside etc.

Keep in mind that time is really end of winter in Northern Europe, so there wont be leaves on trees, or vines etc. If you are looking for beautiful green landscapes you wont find it in those areas of France mid-March. Bordeaux doesnt make sense given its location and to be honest isnt as scenic as the other areas you have listed.

I personally dont like cruises so that wouldnt be something I would ever consider as I like to spend more time in my locatons, not cruising to them.

As for Ireland - it will likey be grey, cold rainy weather. The countryside will be green, but there wont be leaves on trees or anything like that.

If you are happy with that then you cant go wrong really. If you are looking for warmer weather you will need to go a lot farther south.

Or southern Spain but perhaps we might first ask, is the weather much of an issue for you?

Thanks for all of the feedback! We have visited Spain and southern Italy in the past so really wanted something new. We, too, thought of Greece but with current economic conditions and frequent strikes I'd prefer a different destination. Addtionally, I'd prefer to visit the Greek Isles when we can enjoy the beaches at some later date.
We understand March isn't prime for many countries and are prepared for winter coats and gloves but we certainly don't want to visit somewhere the weather will really prohibit us from seeing the sites.
We plan on renting a car regardless of our choice so that our tour will be more self guided in nature. Budget is considered but not an issue (we've been saving up a long time for this trip).
I'm glad to hear that many attractions will be reopening near St Patty's day if we choose Ireland. I was worried about that in both France and Ireland in the smaller cities.
My husband and I enjoy getting to know locals during our trips and aren't always searching for the hustle/bustle but again, just want to make sure we could see the chateaux, castles, etc. on our list of must-sees.

Although me myself I used the term cold, I think that when it comes to weather, what "cold" or "unbearable" or whatever weather might feel, it is a personal call. A good idea is to have a look on sites that have some sort of statistics feature such as http://www.wunderground.com/history/ ,so as to have an idea of temperatures, moisture etc.
99.99% of my trips have to be in winter due to work restrictions and with some planning I always manage to enjoy. Admittedly I am not very sensitive in low temperatures, my only chance to visit Poland was on January/February and many people advised me to hear somewhere in south Europe, but I went with my original plan and had a great time. That said, I met some people who could not handle low temperatures such as -20 C at times, and were really having a hard time... So when it comes on temperatures, it is up to the OP I think...

PS: Greece has many snow ski centers and although winter is milder and sorter in general, March is a very unpredictable month, often very rainy.

Took a trip to Paris and Normandy in the first week of March of 2011. The weather was mid-50's in Paris. Normandy was signifcantly colder feeling. Our trip to Point du Hoc was VERY cold with the wind coming off the Channel. But Paris was fine. Jackets, with no gloves needed.

We were in Paris the first week of February of 2006 and the coldest day was 39 degrees, mostly upper 40's.

We preparing for our next trip to Paris and Loire starting the second week of March next year ourselves. We'll lock in an apartment in the next couple of weeks, then start praying for better prices on airfare!

Julia, before someone hands you your head, please be advised that some folks violently oppose the term "St. Patty's." Use St. Patrick's or even St. Paddy's.

Just trying to avoid a flame if at all possible.

jaja beat me to it. Never EVER St. 'Patty'. (and it isn't just some folks)

Re "Day light hours might be an issue at this time of the year as dark comes early and you can do less in a day! "

Totally not true. The short daylight is in Dec/Jan. By mid March daylight in Dublin, Paris, Rome, NYC or San Francisco are all about identical. W/i 2 or 3 mins of each other, approx. 12 hours of daylight depending on the exact date.

I did not compare daylight hours with Dec/Jan, rather with summer months janisj, but you are right, about 12 hours of daylight on March .
http://www.timeanddate.com/worldclock/astronomy.html?n=78&month=3&year=2013&obj=sun&afl=-11&day=1

I know you didn't compare the daylight to winter - but you said the daylight would be short. If 12 hours isn't long enough daylight that would eliminate traveling anywhere in Spring time. . . .

(I made the point because folks often warn that days are very short in October or Nov or Feb or March, which isn't the case)

mid March is about 12 hours of day light no matter where you are in the world, right - that's why they call it an equinox?

I did not compare locations at same time period, I meant sorter daylight than visiting on eg July. And yes, when traveling I think it makes a difference to have sunrise at 7AM and sunset at 7PM than having sunrise at 5.30AM and sunset at 9PM . Obviously you feel more comfortable to have an early start and you may fit more in a day in second case! Just my opinion.
I am not sure why you stand so much on this point!

OK - to truly beat this poor dead old horse . . . mariha2912, per your opinion re daylight, the only good time to travel is in mid-summer/July.

In truth, July can be a terrible time in many of those countries, even w/ the extra daylight - hot, crowded, expensive.

The problem with March is that it is unpredictable, and often rainy. I've been in Paris at least four different years in March in the last decade and gotten every thing from below freezing to mid 70s (and some years that was in the same week!). I've also been to southern Spain (Costa del SOL) when it rained 5 out of 6 days! Point: you can't know, even if you check a hundred weather average sites.

SO: go somewhere where the weather won't ruin your time, and that usually means a city versus countryside. If you are driving around scenic countryside and visiting small towns (either Ireland or France) and it rains all day will that ruin your trip. It would mine. But if you stick to Paris, and/or some other large city then you can visit museums, shop, sit in cafes, etc if the weather is bad, and do walking tours if it's nice. From Paris there are a number of small towns you can visit by train so you could save those for nice days - you would not need to decide in advance, like you would if you were renting a car for a portion of the time.

In terms of the daylight issue - while I prefer July just for that reason, 12 hours is enough daylight for most people, and if you are in a city like Paris you want a long evening to experience the city of lights lit up.

If you have too much time for just Paris consider adding in another city that is easily reached by train (London, Amsterdam or some other French city). And if you want to do some part of rural France on this trip, probably Provence/Cote d'Azure would be your best bet. I was actually seriously considering the Dordogne this coming March and decided against it for the reasons I just stated - too much risk of lots of rain on a trip that is mostly small villages and scenery.

I am not sure why you stand so much on this point!>

I agree with janis - a non-issue the length of daylight in March - enough daylight for most and isabel hits it on the head - weather factors besides length of daylight are far more important to the selection of where to go - foul cool damp weather is not much fun if outside at least - southern Europe though not hot is much warmer in March and probably a bit drier as well.

janis, I did not say that the only good time to visit regarding day light is July, I said that if for example you are a very early riser or something, you could feel more comfortable to have a nice walk or a hike in daylight on July while on March you'll have to wait one or two hours for such an activity. And you can hang around the countryside or quiet places later in the afternoon if sunset is latter. Just my opinion.
>In truth, July can be a terrible time in many of those countries, even w/ the extra daylight - hot, crowded, expensive.> I have no reason to argue on that, I did not suggest to skip March and go for July. I said you have to look closely on specifics when traveling on March. You may have noticed I travel on winter months myself anyway.


Concerning the weather issue, I agree that March is very unpredictable, but this applies in southern Europe too, I live in Greece and personally I do not find Ireland much worse than here on March. Of course it depends on specific location and pot luck, but advice for rainy days in city with lots to do/see indoors etc (Paris) then trips to rural areas on sunny day, could apply on Ireland too.

PS: I'd like to read what is OP's opinion on this...