Hardtails Are Better said:
I want to slap the Crack'n'fail engineers who came up with the Lefty, and anyone I see riding one. They make NO SENSE. Get the Fox. Ride it. Be happy.
Hah. Very scientific evaluation here. But then, coming from a guy whose handle is "hardtails are better," it's hard to take anything you say seriously...
Now, I'm not going to say that you wouldn't be happy with either one, because they're both awesome forks. However, I think the Lefty is the most amazing fork out there. One thing that few people mention (and maybe don't realize) is that the Lefty can be completely rebuilt. That is, if you happen to have problems with it, you can have it serviced by C'dale (if you know somebody at an LBS, it's not that expensive), and it will be AS GOOD AS NEW. Not just better than it was, but just like new, because ALL of the surfaces that wear are replaced. Try that with a bushing type fork. That has more appeal to someone like me who likes to get quality stuff an then make it last a LONG time. If you regularly upgrade, it's a non-issue.
As for confidence on the trail, I've never felt more confident than I have on a Lefty. They do seem a little weird at first, it's true, but the control is so amazing. I guess there's something to the "square" design.
Unless you're racing or really want to focus on climbing, I'd highly recommend getting a Lefty with TPC+ instead of SPV. I still think that TPC+ is one of the best, if not THE best, damping system ever put in a fork so far. Just my opinion though. Others may disagree.