If you have a 1098s already I can't see the point of either. If you want to ride fast, you take out the one you have. It makes more sense (from my personal point of view) to get something totally different that delivers thrills in a different way or has some other use. So I'd get a Monster, Hyper, Diavel, Multi, Sport Classic or something like that. The749r and the SPS are going to deliver thrills in the same way as your 1098s - cornering on your ear and giving it the beans out of turns.
was offered a 996 sps a couple of years ago for 6k. bought a 1098 instead as I was worried about the rocker concerns. I now could hire someone to boot me in the ass for being so stupid.