If it's a question of what's more secure, I'm betting that within two years we'll have at least one working PoS system that's demonstrabily more resistant to attacks than PoW.
I betting within two years no one will be having this debate and PoW will have crushed everything else into oblivion.
And I am also betting it won't be Bitcoin.
It will turn out that PoW is absolutely essential. Everyone will go "a ha" and that will be the end of the debate.
(I might be a bit too optimistic...we'll see...)
If PoW is what we have, I'm fine with that too. I stongly dislike the way Bitcoin mining is headed though. I think everyone who isn't one of the few running one of these 9 figure operations must as well.
A billion people mining on their low powered mobile phones would be nice. As was discussed previously in this thread.