Choices: Syringe Gun, Crusader's Crossbow, Overdose, Blutsauger
Keep in mind that my perspective is that of a 6v6 competitive medic.
Personally, I don't think the xBow is a good choice. It's a lot of fun, and can lead to some awesome frag/distance heal videos if you have accuracy, but in terms of defending yourself from a scout when you're alone, it's just not as good as the needle guns.
In a similar vein, it takes a special kind of medic to use the Blutsauger effectively. Passive health regen. is an attribute completely unique to the medic, so you have to be careful of limiting it so severely. There are some great competitive medics that use it well, but for most people I wouldn't recommend it. Health packs should actually be saved for your teammates when you can't heal everyone at once. They shouldn't be used to heal a medic who has taken spam that s/he shouldn't have. (Obviously if you need the pack, you need the pack).
In competitive TF2, you'll see some medics using xBow and a few with the Blut, but many will choose the Overdose (some like me use stock). Here's why I don't think the overdose is a good choice:
Let's pretend that the base medic primary has none of the advantages of stock or the Overdose. You get to choose: +10% damage, or +x% speed increase while the overdose is equipped, where x is 1/10th your uber percentage.
Both of the advantages of the two guns only work when they're equipped. If you think about when you're going to be using your primary, most often you will be alone, trying to escape and enemy. "AHA!" you say, "surely I choose speed then. If escape is my goal, I want to move as quickly as possible!"
Well, sure, speed is nice, but in 6v6, who are your opponents, again? Oh, right, the three fastest classes in the game, two of which also have nice speedy projectiles. Even with the maximum speed addition of the overdose, you will not outrun a scout or a well-placed rocket.
Furthermore, you should never be taking advantage of the full 10% speed boost anyway! If you have 100% uber, you should use that to escape. And if you have more than 75% uber, it's probably less risky to try for the ubersaw than it is to try to run.
Personally I'd rather have the extra damage with each needle. A nice burst of needles can be very discouraging to a chasing enemy.
In short, the benefits of the overdose are not as applicable as people think, and having a bit of extra damage in your needles is probably more useful.
Edited by Savage, 07 July 2013 - 07:46 PM.