I'm sorry if this sounds rude, it is not intended to be in the slightest, but this subject has always irked me. My dad is very opinionated and feels that mares are just not as good as geldings because of ONE mare that we had. That is obviously NOT the case. Yes, some mares can be very "mare-ish" - for lack of a better word - BUT I have known many geldings that act the same way. My answer is this: it all comes down to the individual horse. None are the same. AND it comes down to your personal preference. - that is just my opinion though.