Team Peeta!!!

In my case I would choose Peeta because he really loves Katniss and takes care for her.

After the first capital I obviously was for Gale because he and Katniss are best friends. She understood his feelings and thoughts about the Hunger Games and they had a lot of fun by hunting in the forest.
But it seems like Peeta loves her too and would do everything for her. He protected Katniss in the arena insofar he got together with the other tributes from district 1 and 2 to  keep them away from Katniss. That boy would risc his own life for Katniss. Not every boy would do this and I'm not sure if Gale will do this too. That's an important point why Katniss should choose Peeta. I think she loves Peeta more than Gale because she would rather die as win the Hunger Games without him!