The C-17, whilst quite noisy, is a good jet to fly on Space-A once the aircraft commander lets you out of your sidewall seat. Those seats aren't very comfortable; the cockpit seats are much, much better
. Once out of your seat, you can lay a blanket or a sleeping bag down (depending on floor space available) and take a nice nap. The cargo floor is heated and is way more comfy than the ol' Tube of Pain (C-141). Since the jet flies slightly nose-high, your warmest part of the cargo compartment is in the forward section closest to the loadmaster station. Anything aft of the wings, you'll need an extra blanket, especially by the troop doors. A side note: the gap between the cargo door and the ramp makes a great place to put the drenched boots of "dollar-riders" who take them off whilst napping in bunk; the boots tend to turn into blocks of ice quite quickly
. Another convenience are six 115V wall outlets along the sidewalls. While you can plug a laptop or other device into them, it's not exactly legal according to the vol3. However, I've never seen anyone get yelled at for it.
-135 is not as pleasant to fly on. You have web seats and the environmental system is no bueno. Your feet will freeze and your head will bake. It has a couple sets of crew bunks in the tail, with one bunk above the other. The guy in the top bunk will sweat his butt off; the guy in the bunk four feet below him is shivering despite a blanket and a winter jacket. Unless you have a very warm sleeping bag and a jacket, don't sleep in the boom pod. It gets wicked cold down there.
The C-5 I flew several years ago gave me a good trip. Granted I was stretched out on the three seats in my row, but it was great nonetheless
. Too bad my C-130 rides weren't as good. Being crammed into a Herk cheek-by-jowl with at least 70-some other dudes is not fun. Plus, the enviro system didn't work for about half of the two hour flight, adding to the misery. And yes, it was noisy and bumpy, too. Thank God it was at night in November when we took off from Kuwait; I'd be hating life if it was a daytime flight in August!