Don't forget about the Polaris Octane as an option too.
My brother's about 270 to 280 and that's what he's currently riding. He used to have a SXR, which was definitely better than the 650sx that he was riding years ago. The hull was a great size for him, but he was never really fond of the bulkyness and weight of it. The only mods he had done to the SXR was an extended ride plate, a different intake grate, and a Factory wet pipe. Last year he sold the SXR and switched to the Octane. The Octane is definitely his favourite boat of anything he's ridden. Plenty of power and also a lot more buoyancy than most other boats aside from the SXR. I think the added buoyancy is definitely the big difference in "managing" and being able to have a good time. He's ridden my square nose SJ around and some of my friends round nose SJs, but he doesn't look right on it, and they don't seem to be buoyant enough for him to really have a good time. Him on the SXR or Octane is more like the average rider on a SJ as far as I'm concerned.
I know this is really a SupeJet biased site. I'l admit I'm generally biased to the SuperJet (and Octane) myself. But I really think in the case where the rider is around 280 lbs, they are best on a wider hull with some extra buoyancy that comes with the SXR or Octane. In my opinion, and my brother's, a superjet is not the right choice in this case.