I've got the '08, which has the 215HP motor. If I was buying a newer one, I'd
try to get the 255HP, just because I could. But that wouldn't be a deal-breaker for me if there was a definite price break that made the 215 worthwhile. I typically run 2 adults, 2 teens and one pre-teen in the boat and the boat does fine, goes as fast (probably faster) than the rest of the family wants
and has more than enough power to pull the three kids in a three-man tube. You don't go that fast pulling a tube, skier or boarder (15-20mph tops), so the extra power would just be for blasting on the water with everyone on board.
I've had 4 adults, two teens and one pre-teen in the boat, probably near max capacity. Yeah, it didn't take off like a Corvette, but again, I got going fast enough for what people wanted/enjoyed.
In reality, if you're a real speed-demon, the 255 probably wouldn't satisfy you enough, and you'd want to look at another model with a pair of 215's, 255's or 260's.
Check the book value on the difference between a 215 and 255 and try to get a deal that's even better on the 215. Use words like, "nobody really wants the 215s, so it will be harder to sell" and stuff like that.