I would have went with Sakura. But unfortunately I clicked Naruto hastily without thinking. Heh.

]Sakura would have been an interesting Candidate, her brilliant chakra control and knowledge would have come in very handy. However I question her mental stability. Imagine her Inner Sakura keeps on fighting with the Kyuubi inside her. Hehehe. Or they'll be best friends and have fun time.

But Sakura in times of trouble, I think she makes very poor choices. She don't have the creativity unlike Naruto to overcome stuff. Sakura would just hold her kunai, close her eyes and say "Please Mister DOn't" Like protecting Sasuke versus Gaara. Some help. Neither does she have the strive and determination like Naruto to keep on pushing.

I choose Naruto, for the simple reason, he doesn't give up.