I have an all-weld crestliner aluminum sport fish. Really like it. But just for the sake of argument I would not be a bit affraid of a riveted aluminum boat . The thickness of the aluminum is probably more important than weld vs rivets. Rivets can actually be stronger than some welds. There are literally 1000's of older starcraft, crestliner and even lonestar riveted aluminum boats from the 50's, 60's and 70's out there that are just as tight as the day they were made. My dad had one (62 starcraft) and I have a friend with a 1955 lonestar both still good. The bigest problem with these old aluminum boats is the transoms were reenforced with marine plywood that eventually rots making the transom weak. Replacing the transom wood is quite a chore, but can be done by about anybody with a little bodywork experience. The big + on the newer aluminum boats is that the transoms are also all aluminum that is very thick (not all though, some still have wood)