I went with the Common from AVM (004). He's not the most powerful, but features a design that allows him to be damaged and still be useful as a primary attacker.
The Avengers Initiative TA is a huge advantage against the plethora of Stealth. Like all Thors, he sports Impervious, but has it placed in a spot that allows him to be used more aggressively early on, take damage (from pushing or an attack) and become even more effective.
At 200 points, he's just cheap enough to allow decent support to be added to your force @ 300 points.
I am not a fan of the AVM Movie Thor, due to the lack of comic accuracy in the Movie, and since when I read Thor, it was when he had his classic traditional costume, with blue pants and yellow socks on, so I hope they may another Thor, that will be the most powerful Thor yet, but only flying and in his traditional classic costume, which they should have done for the 10th #016, since that sculpt was awesome and the best so far for a Thor in his Classic Costume.
I also think, if they had Thor wear his helmet in the AVM Movies he would look more classic and formidable, as he should look.