One thing to remember is that both Uncouth and Uneducated can be bought off during character creation if you so choose. Centaurs really don't have a lot of advantages - only two Attributes get a +1 boost, and they don't have much in the way of special abilities, either. And with how incredibly distinctive they are, they won't be very practical for most campaigns. I am not that well-informed about Missions play, but it seems to be "traditional" shadowrun. A centaur would be better for a campaign set in a semi-wilderness setting (NAN, smugglers, paracritter hunters, etc.). Their main ability is their Search power, so combine that with the Outdoor skill group and you can have a decent bounty hunter or guide. Even so, you will be behind the power curve of the other players. Centaur is a choice that is very sub-optimal from a numbers-crunching POV.