Hey Astern! Well, if your playing MMO's such as world of warcraft it would be useful if you can have the extra buttons because with the'se extra buttons you can customize them into macros and that is very usefull on a game like world of warcraft so for that I recommend the razer naga. The razer naga is in my opinion one of the best mouses, it has an awesome design that glows up and has the extra customizable buttons and the mouse is super comfortable for your hand!
If your playing over MMO's such as shooter MMO's you dont really need that many buttons but the extra buttons are sometimes also usefull as you can customise the button to do different things for example on an MMO shooter if i wanted to do a punch I would press the 1 on my mouse, so for that I would buy a razer deathadder. The razer deathadder is a stylish comfortable mouse and is quite cheap compared to other gaming mouses.
if your playing general MMO's and dont need very much buttons and just want a comfortable cheap reliable mouse, I recommened the gigabyte M6800.
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Happy Gaming, and enjoy your gaming mouse!