I've only seen the movies but I'd choose Whis as my sensei.
He's the strongest of the strong (or pretty close at least) and can attack faster than a persons brain can tell their body how to react.
This guy is crazy strong. Like can take down someone who can take down Goku strong. And if I could become strong enough to even put up a fight against Goku, I could die happy. Whis can put up with Beerus' antics, so he's definitely got a lot of patience. Which is good because I can only do 5 push ups as is lol And I highly doubt I'd get bored training with Whis. Learning how to manipulate objects would always be a plus, too!
All I would have to do is bring Whis and Beerus some delicious mexican food and voila`, my training begins!