Some people have much stronger and more nimble tongues than others due to physical differences (e.g., tongue size, the length of the tongue frenulum, etc.). But this is the case for the hands as well, which is why people have different input preferences and different gameplay preferences.

Personally, I think I would prefer a mouth controller over a traditional controller. I am very prone to tendinitis in my hands, plus I have small hands and short fingers, and can't play twitchy games well because of it.