The comparisons aren't really that important (to me at least). It's possible that these products can (and will) coexist. What is with the need to pronounce a winner as soon as possible? A product like Google+ is going to take a while to gain a user base and mature (just like Facebook). Launching in the shadow of a massive competitor (just like Facebook did VS MySpace) doesn't call for an instant death-knell.
I'll repeat something I've said here before. People said the same thing about Chrome weeks after it launched. It. Took. Time. How about sitting back and letting things shake out a bit before pontificating?