If it has to go checked to the third world, and price is no object, then I'd suggest a Titan hardside spinner. If softside will do, then I'd suggest the lightest thing you can get from Eagle Creek; duffel or square, whichever he likes best. If you need to stick to a lower budget, then try to find a Delsey Helium bag at a discounter like Marshall's, TJMaxx or Ross. Go for a lifetime warranty if at all possible.
(I agree that Tumis are great bags, but they are known to be expensive, so they are attractive to thieves, too.)
Samsonite bags are made of durable materials, but lately they have been having a lot of problems with badly made handles; it can be a hassle to have to have them sent back for repair.
Whatever you do, make sure that you do not go above a total size (L + H + D) of 60 inches (the limit is 62", but a crammed suitcase normally will go a bit larger than it's spec'd dimensions). Also, stay under 10 lbs. empty.
For a carryon that will be used internationally, don't go bigger than 19".