Of course, that is high season, so rates will be high and availability limited. Can you give an idea of your budget, who is traveling (2 adults? any kids?), and what you like? But, for Jasper, you might check Patricia Lake Bungalows: http://www.patricialakebungalows.com/units_rates.html

You can do the Icefields on the drive from Jasper to Banff. That will make for a full day's travel, giving that you will find plenty of other places to stop and gawk/walk/take photos.

I don't see a problem with your allocation of days, but again it really depends on your interests.

Emerald Lake, Takakkaw Falls in Yoho National Park s/b on your list. Short trip from Banff.
From Jasper to Banff there's lots of beautiful stops including the Icefields.
If you have an extra day before heading back to Calgary, go to Waterton. Stop at Frank on the way.
As a city, Banff is nicer than Jasper, but in any way do not spend any full day in either city. Plan to have your dinners there though. More options that way in Banff.
Jasper is quite boring in my opinion.

http://www.fodors.com/community/canada/canadian-rockies-trip-report.cfm?21

Here's how we divided up our time in the area. Hope this helps. It is one of our favorite places to visit.

I think you will enjoy Jasper. We have never had enough time to spend more than 2 nights there. If you spend 3 nights, Alpine Village seems to be a nice place to stay--they have a 3 nt minimum stay. We enjoy hiking Maligne Canyon, walking around Maligne Lake, Angel Glacier.

In July, Banff can be very crowded.

If your other plans fall through, there is a nice HI hostel about 3 miles SW of Jasper near the start of the Icefield Parkway. They do have a few private rooms in addition to the coed dorms. Their kitchen/dining room has a nice fireplace.
I second the hike down through Maligne canyon

Yes. Banff is much more "touristy" and crowded than Jasper. We had always stayed in Banff and were blown away on our last visit, when we stayed a couple of nights in Jasper.

You could spend a day in Banff just shopping. Yes, it's in the park, but it is a compact little shopping mecca with a bunch of (mostly casual) restaurants. Then when you are ready to get away from that, go on to Lake Louise and beyond to Jasper.

There is a nice HI hostel about 3 miles SW of Jasper near the start of the Icefield Parkway. They do have a few private rooms in addition to the coed dorms. I second the hike down through Maligne canyon. You could spend a day in Banff just shopping. think you will enjoy Jasper. Alpine Village seems to be a nice place to stay.

Thanks, everyone. Your replies were very helpful!

There are 2 couples traveling, one in their early 40s, the other in their early 50s. Everyone is in reasonably good shape. While hiking is not the main focus, we would definitely like to make it an 'active' vacation.

So I will come up with an itinerary based on all of your recommendations. Once again, thanks for your input.

Just a comment here and this may be obvious to those familiar with these places, but I think can be confusing to those not familiar. The names Banff and Jasper in each case refer to both large National Parks, and to towns located within those parks.

Both National Parks are spectacular with subtle differences in their scenery. The actual town of Jasper I found to be more-or-less a tourist service centre, strip malls, souvenir shops. motor hotels and restaurants (although there were a couple of pretty good ones I remember). The cruise on Maligne Lake is popular and just scenic driving around the park with stops for picnics and short hikes is wonderful. Good wildlife watching - a herd of Wapiti (Elk) hang around the outskirts of town, and Moose, Bald Eagles, deer sightings are common - even the occasional Black Bear (do not approach any of these closely for safety).

Also as recommended, you can take a full day to enjoy the drive from Jasper to Banff on the Icefields Parkway, stopping at the Athabasca Glacier of the Columbia Icefields and doing an Icefields tour on a specially designed vehicle if that interests you.

It's been a number of years since I've visited the town of Banff but I remember it being larger than Jasper, more services and attractions, but also busier as a result. Again - scenic touring and picnicking is great, with visits to Lake Louise and as recommended Emerald Lake and Takakkaw Falls in adjacent Yoho National Park. There is a famous spiral railway tunnel in that area too which you can view. More wildlife watching - scan the forest margins and open areas and wetlands as you drive.

I think someone mentioned above that your timing is in the busy summer season and from my past experience, rooms can get booked up well in advance so you should look into this asap.

I was just in Jasper this past week and I would agree that the "downtown" such as it is is basically tourist central with plenty of souvenir shops, pizza restaurants, etc. The best thing about the town is, IMO, the view of the mountains outside of it.

There are webcams in both Banff Township and Jasper - you might check those out to get an idea.

In the town of Banff, it's much more sophisticated - lots of shops, restaurants, etc. - and traffic. It's just a couple of hours max from Calgary and so you get the casual day trippers. Here you can shop for higher-end clothes and dine at nicer restaurants. And there are a lot of people/traffic.

Jasper is less congested, and the shops tend to be less pricey. The restaurants are more casual. There will be a noticeable number of tour buses, and they will offload their passengers at the hotels along the main drag. I'd avoid staying there. There is a pizza place in Jasper that I think makes fabulous, brick-oven pizza - but sophisticated it is not.

Both places are great. For us, having been to Jasper only once and Banff a number of times, of course we want to return to Jasper. Were I you, I'd try to visit both places for this your first visit - then you will be able to plan a return trip to suit your interests.

We loved hiking near Moraine Lake. Even better, renting a canoe there for an hour was some of the best money we spent. At Lake Louise, the hike to Agnes Lake and the tea house is memorable although steep. I will always remember balancing a muffin on my head to keep it away from the chipmunks.

The scenery is spectacular and you'll find yourself stopping frequently for just one more spectacular photo no matter where you are.

<I will always remember balancing a muffin on my head to keep it away from the chipmunks.>

Yes, but that wouldn't deter those pesky whisky jack birds!