It is my opinion that European players are more dedicated to begin with, so you'll have a better foundation to build a sound community upon. Brazilian players, while abundant, are more likely to be very indecisive and reckless (in regard to botting). Either way, Brazilian players will play your server, especially if it becomes popular. ShadowCores was hosted in Poland (if I'm not mistaken) and it had thousands of players, a lot of which were Brazilian.
It's important to consider what you want: USA or EU are the best options.
