Ranked from most to least comfortable (IMPO):
1. PC gear (like wearing normal shorts and a T-shirt, only you need to tuck the shirt)
2. Flight suit (feels like wearing pajamas with boots)
3. ABU's (somewhat loose fitting and also warm in winter)
4. Blues (tight fitting + pants are a bit uncomfortable, but they are relatively lightweight and cool)
5. Service dress (looks really sharp, but can be hot in summer and somewhat restrictive of motion)
6. Parade dress (hot, very restrictive, and hard to put on, but it is also the most formal uniform and looks really neat in parades)
There are different variations of these uniforms, too (such as service dress + overcoat or blues + parka), but these are the 6 standard cadet uniforms. Hope this helps and feel free to PM me if you would like.