Learn "Working class hero" (or maybe "Wish you were here"), you can hammer-on to your heart's content
I certainly wouldn't consider myself a proper guitarist, but fwiw: I'd probably play it with the hammer-on, that sounds better to me (and doesn't Justin do that as well once or twice?)
Btw: that open C with the first finger (2nd string) lifted off is a Cmaj7
Edit: One thing, though. If you play it with a hammer-on, you really need to nail that note down, it's vital to the riff. That's probably the reason why Justin goes for the picked note here (wild guess on my part).