after thinking long and hard on it (ow! you makeded da brain hurts! okay, so actually it wasn't long at all, but it's early. *L*), here's my take on riveting vs stitching.
riveting is decorative (a nice byproduct), quicker, easier, cheaper (when comparing machinery costs and even timewise, especially if doing it by hand), easier and quicker (usually) to replace if need be and personally I think stronger when done correctly. stitching can be nice on some things, but to get the strength needed with some items you've got to do a lot of stitching and that can actually be detrimental at times to the strength of the connection since there're a lot of little holes in one area that were formed by basically tearing the leather with a needle instead of removing some cleanly with a punch. I know it's different material, but the effect is still mostly the same. take a piece of vinyl and punch a hole with a hole punch, then poke a bunch of holes in a row with a needle beside it. now pull at the edges. the stitch line will tear before the punched hole will.