I have been around various parts of the world in the last 13 years (65 countries/16 US states/over 100 flights). I have seen all sorts of stuff coming past on the luggage carousel. There is no specific way to go. Tough plastic is good, soft sided is cheaper but liable to more damage. The best case I have I bought was a Carlton hard plastic bought 8 years ago in a sale for �40. The handlers at Miami and JFK have not yet managed to remove the wheels, handles or hinges. This cannot be said for any other pieces I have where stanlye knives have clearly been used in the sorting process.