i have tried both and i own the QC3. as others have said, the QC2 has better sound and is more comfortable - the QC3 can get sweaty after a while and it does squash your ears a bit. but saying that, the 3s are still a fantastic product, and the smaller size makes them a better choice for the traveller. they easily fit into a jacket pocket without sticking out conspicuously.
wish i had known about the john deere's tho, they sound well cool. the shure in-ear products are also getting good reviews which would be a better solution for sleeping on your side.