I've been playing a few 5-Card Draw MTTs on PokerStars recently, and I like the game. It's a pretty easy game to pick up. There isn't a whole lot of aspects to it, especially in limit.
I do have one question regarding the game though. I'm not sure who plays it that much and knows much about it, but what I want to know, is is it better to draw 2 or 3 cards when you are dealt a pair?
I'll give a quick example situation to illustrate my question better.
You are dealt

Would it be better to keep the

and draw two cards, or just the two 10s and draw three? Obviously, the two different draws depend on what you want to get. If you want/need to get a set, you should draw three and ditch the ace. If you want to get two pair, it seems like it would be better to keep the ace. In a game, you will be able to access what you need compared to your reads on your opponents hands.
But my question just deals with the best chance of improving your hand, disregarding any information about opponents.