In Europe: with breakfast, always. I can have my three cups of milk coffee, fruit, muesli, bread, honey and juice that will sustain me easily me until 1 pm. After breakfast, I can brush my teeth and get ready to go. It's part of my travel routine and I stick to it unless the breakfast cost is exhorbitant.

The size and composition of the breakfast tends to vary by country. The price tends to vary by the type of hotel. If you stay in pricey hotels, breakfast will be pricey. It pays to do research.

I prefer having breakfasts.

for me it's mostly without, because the food tends to be very basic and I would much rather run to a local bakery or have a breakfast picnic at a park, But it all depends on where you are and what are you're plans, if you have a tight schedule and are only staying for one night then yes, breakfast is great cause it saves you some time, but if your are not in a hurry I would recommend enjoying your breakfast outside of the hotel/hostel.

I mostly prefer Hotel with breakfast, mostly it depend on where you are and what your plan. I don't eat a lot but like having the option of something quick.

For me and my partner it usually depends on price and budget. The last hotel we stayed at in Madeira had breakfast included in the rate and they had quite a selection every morning that was all really good quality. However, I tend to struggle to eat in the mornings especially when on holiday due to a nervous tummy so I felt as though I couldn't take advantage of what was on offer. We've stayed at other hotels in the past that didn't have breakfast included and instead we've just stocked up on cereal bars etc from the nearby shop which saves us quite a bit of money and means we don't have to worry about being up by a certain time. Generally if it's extra on top of the room rate, we go without.

Travenix
 

Eating breakfast might be nice for your diet. But breakfast doesn't cause weight loss. So it operates better for some individuals to skip breakfast. ... Several studies have shown that skipping breakfast has no impact on the complete amount of calories you burn throughout the day.

With usually. When we travel on vacation we try to stay at a nice hotel and get a breakfast with it.

I disagree completely. You should have a good breakfast to start your day and studies have also shown it jump starts your metabolism which of course is a calorie burn. Skipping meals can slow your metabolism

I agree. And occasionally they are exceptionally good.
We had an amazing breakfast at the Sheraton by Valley Forge.

Also worth noting, breakfast is a godsend if traveling with kids or teens. You don't want them tired out or mad before you arrive at your first site that day.

Good point, 5alive, about traveling with kids. Having a breakfast on-site eliminates the problem of having to find a restaurant first thing in the day, to suit everyone.

You don't want them tired out or mad before you arrive at your first site that day

The same applies to many of us adults. Hangry and holiday don't mix!

Beakfasts vary between hotels in the same chain also. We tend to just have cereal, maybe some fruit and a cup or two of tea. If the hotel rate is cheap enough we will have the breakfast. Otherwise we will scout out a supermarket the night before.