Does he drink alcohol?

I am in no way implying that looks matter more than experience. I am saying that all things being equal, if neither actor is truly better than the other, I would go with the actor who at least looks like the character I am casting. Even with Josh's experience, I don't think he is a good actor.

Obviously, the producers and the author probably saw something in Josh that helped him win the role, or the role could have been "bought" in exchange for another industry favor. Either way, I don't always trust the casting department to what translates well from book to screen. For examples:

Kristen Stewart is horrible as Bella in the Twilight movies. In fact, all the vampires were miscast but author Stephenie Meyer inexplicably supported the cast. Some idiots just cast Jamie Campbell Bower as the devastatingly handsome Jace Wayland in "The Mortal Instruments" movie, in which Jamie is in no way attractive but author Cassie Clare thinks he will be great. The Harry Potter kids are hit and miss.

I'm not 100% sure how Alexander would have fared as Peeta, but after seeing Josh "act", I think he would have done better. I know Alexander nailed Cato, but Josh didn't nail Peeta. Physically, Josh looked like a hobbit. That alone makes me wish Alexander (or Jeremy Sumpter) would have gotten the role.

Maybe Alexander is too tall for Peeta, but likewise Jennifer Lawrence is too old, too tall, and too healthy looking to play Katniss. Jennifer is an excellent actress (I loved her in Winter's Bone and no she is not overweight) but she didn't nail Katniss. She was miscast for the role, however she came across better than Josh.

Sometimes actors can overcome their physical limitations and completely embody a role and take a movie to another level. Neither Josh, nor Jennifer for that matter are at that place in their careers. To me, neither of them were believable as starving teenagers from a hard luck district. Not by a long shot.