I have a quite chunky (hard plastic of some sort) Samsonite which is probably 20 years old and still going strong. Has survived a huge amount if long haul bashing. Don't use it that often because it is quite heavy. My newer ones are polycarbonate and much lighter, but don't look like they will last as long. Not tried aluminium ones, but it seems that they potentially get knackered faster because unlike many plastics/polycarbonates the problem with metals is they deform (permanently) with a hard knock.