I do 100,000 miles plus each year, and have spent more money on suitcases than I care to remember. I want, nay, demand
lightweight, my favourite Samsonite is 8 kgs, which is 3kgs too heavy
Good compartments to stop things moving about
a foldable suit / shirt carrier that reduces the creasing without adding a lot to the weight
extendability, a set of zips that allow the case to be deeper
sensible wheels, preferably four, preferably not modelled on a shopping trolley
good height of extendable handle, I want to put a bag on top and still be able to steer the damned thing
colour is unimportant, sensible people tie odd coloured ribbon to the handles
external pockets are a nonsense, they are just bits to get ripped (I can live one large pocket)
May favourite for compartments was a fold over Dakota, but it weighed 12 kgs