I still have no idea which I want :/ I do play a lot of League (Like, almost exclusively ATM) so which do you think is better? Also, how easily did you learn to use different buttons?
The fact that you play MOBA games in general points towards the Naga over the other two, but you might prefer the ergonomics of the Taipan or Deathadder
If its just League that you want it for, you could go with the Naga Hex, which has a six button keypad instead of twelve, but I find that having the extra buttons is useful for things like the courier in DoTA and Recall in League.
Regarding learning to use the different keys, it does take some getting used to. You might be a little bit slower with item usage and such, but you can adjust pretty quickly.
By the way, the keypad isn't actually its own separate set of keys. Each of them is bound respectively to one of the number keys on the top of your keyboard, 1 through =. 1 being, well, 1. And = being 12. A sort of keybinding within a keybinding