Pads may keep you warmer but they need some sort of vapor barrier between them and the ground/tent floor/etc... Cots may be more comfortable (that's a matter of opinion though), but they add bulk and weight. Personally I'm a minimalist so I say go with the egg crate pad and sew a piece of waterproof/resistant backing around it, although you could probably buy the same thing for less than it will cost you to make it, and set up on some long grass that you matt down. I don't really like the "air" pads, thermarest and such, you end up with pockets of air in all the wrong places and still have to deal with ground hardness.