I couldn't hang with engineering so I can't address the specifics Bill & Wouter and everyone else has layed out.

I know my SC17 is an excellent sailing boat and I love it. I have also seen the photos of the new ARC 17 and spoke with one of the "test pilots" from Pensacola....apparently it is awesome....I've made some mods to mirror the ARC (sq. top main & high aspect jib), now if I can just get it dialed in.....