I like full length Thermarests. I had a 3/4 length ultralight and found it just made me feel weird having my feet hanging over the end. I lost it somehow so I bought a full length standard which is nowhere near as compact, but it's more comfortable and another advantage is if I sleep outside (e.g. on grass), the foot end of my sleeping bag doesn't get wet from dew.

Generally all the Thermarests are nice and the widest and thickest ones are the most comfortable of all, so it's a matter of what you're willing to carry. I don't have any trouble with the full length standard strapped to the outside of my pack. The real luxury model is called the Camp Rest which is 6" wider and almost 2x as thick. It still weighs under 3 lbs so carrying it isn't crazy, but I decided it was bulkier than what I wanted to deal with. It's almost like sleeping in a real bed though.

Finally, Marmot Mtn Works used to make sleeping bags with an integral theramrest-like pad. I don't know if they still do.