I'd say it's the same Puck.
Given that Marvel timelines aren't always simultaneous my guess is either that

a) the Wolverine Goes To Hell storyline was before Chaos War and that Herc brought Puck back too.
or
b) whatever Villain is behind the Unity Party/behind Fear Itself brought him back.

And in regards to the 'time in hell changed him' it'd probably have played with his mental state a lot.