Voltage for an Arduino button box

I am completely new to Arduino but I have looked at some videos and decided that I want to try to buy a button box for playing Star Citizen.
All videos suggests that I should use the Arduino Pro Micro as controller but it seems that there is a 3.3 volt and a 5 volt version.
Which one should I choose? or does it not make any difference?

Hope you can help.

Best regards

Think you need to say a bit more - how is your button box/game to be connected together , is the game on a PC ?

I would go with the 5V one, although ultimately either will do..