Your chances of surviving the New World are very slim unless you are under the protection of one of the four Yonkos. So the question is, which one of them would you want to work for?
I would work under Blackbeard. For the time being, the guy is seemingly invincible with his two Devil Fruit powers and his ten battleship battalion. Plus, he seems to be a pretty stand up guy and having him as a friend would be awesome.
Not to mention, if he's beaten by Luffy, falls into the water, and dies, I can swipe his Dark Dark Fruit and slip away into obscurity.