Definitely Google+ is better these days for SEO. Its a powerful weapon to boost search engine rankings.
G+ and FB both have their own impotence, it is not good to compare them. it totally depends on the guys who use them, if any one very friendly with FB then FB is good for him or if friendly with G+ then G+
Google+ was created to combat facebook. Google+ still need to develop more of its service. It may not be a prominent as fb but still it has lots to offer.
Is it really the reason why Gplus was created? To combat FB? I don't think so. Gplus has its own business plan and its own strategies.
Google has it's own plan for business but Google+ was sure to combat Facebook and other growing social media where Google was lacking with Orkut an dother creepy like Google Buzz and Google Freiends connect.
Both are great. You just need to be smart and connect your site with both and make those platforms work for you. That means you need to come up with some engaging ways to get people go from your Facebook and Google+ page to your site. I think that the content is the key there.
Proper SEO would have both. I'd say they probably give close to the same when it comes to "authority" passed along. With it only taking a few minutes to create a page for each, why not just go with both?
Yeah of course, I've asked http://blackcatseo.ca to boost my G+ and trust me, it made more ORGANIC impact than facebook history....