What suitcase do you guys carry?

Not really related to anything gay, but what suitcases do you guys carry? Soft, Hard, Aluminium? Any specific brands? I'm in the market for a new one, and i'm not sure what to buy.

Also two wheels or four wheels. I live in a big city so I don't have a car and I've heard 2 wheels is better on uneven payment, but i've never used one so I cant be sure.