ACB robes for me. AC3 close(VERY). ACB was the only robes that didn't look like a bear after full armor equip. ACR robes pissed me off. Far to bulky no matter what you did with them.
i always thought AC1 robe was ugly as hell
I always liked the simplicity of Altair's outfit, but it was very dirty looking. And in ACR, Altair's outfit made him look fat. ACB was great because it was so white and it contrasted a lot, but it didn't really match the environment. ACR robes were fantastic. The blue color it gives off at night and the grayish color in the afternoon. Connor's outfit is nice, but something about it I don't like too much. I will have to go with AC2 robes.
Connors in AC3 are by far my favourite. They just look awesome, and the off white / light brown sorta colour is awesome. Second favourite would Brotherhoods, looks so awesome and stylish. Next would be AC2, again very stylish but not quite as cool as ACB. Next is AC1, the physics on the robes were great but they looked **** in ACR.
Lastly by a long mile is ACR. I hated how he looks in them, though that could be due to the character model, he had a funky posture in that game. Regardless I never liked the ACR robes. Love the Ishak Pashur armour (whatever it was called)