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...)