My highly unscientific testing has the SW right at about .2mph slower than the Whiplash in flat water at race pace over short distances. The gap may grow slightly at longer distances. Pretty good considering the Whiplash is both narrower and more flat water focused. I would certainly rather be stuck with the SW at a flat race than with the whiplash at a choppy one. For now I'm using the stock fin, I haven't tried to swap anything in yet. The board tracks really, really well but I have to get waaaaay back on the tail to pivot turn it. Don't know how much of that is fin and how much is just the board itself. My 404 is like that, it will not turn unless I get all the way back. I like that the deck pad goes all the way back on one hand but on the other hand I also cant put a kick pad on it to reference where to stop when I'm moving back.
Looks wise, the board breaks necks, everyone has a comment on it. The Whiplash, bristling with all the latest multi fin tech and snazzy carbon brush finish is invisible next to the Sidewinder. I do wish they still did the black deck pad instead of the grey but that's a pretty minor nitpick.