He's pretty enough certainly, but for me it was a toss-up between Glenn Howerton and Taylor Kitsch purely because they can both have that little bit of arrogance about them - a sort of "Yeah, I know exactly how good I look" air about them.
Kitsch is the better of those two, imo. Clean shaven he had the pretty-boy thing going much better.
Matt Bomer is my go-to as well, he has the same touch of arrogance but also the ability as an actor to look like he has lots of confidence that is all a mask. That and his White Collar Character basically /was/ thomas, just with "vampire" replaced by "Con-man". The problem is he's quickly getting too old for a Storm Front vintage Thomas where they'd likely need to cast the character, rather than the 15-ish years later that all my mental images are stuck at.