Everyone has given great advice. My first horse was a qh and she was crazy! But she was also a 3 year old with very little experience, so that had a ton to do with it. Qh are very smart and are known to test you if they know that you don't seem very confident. Tb will do the same, as my horse is used for lessons on occasion and is only used for the more experienced riders because of his tendency to try and take advantage of people. He won't even attempt it with me though.
Geldings seem to have more even temperments. When mares go into season they can become stubborn and moody so I prefer geldings myself. :) But not all mares are like that, I've just had that experience. Also, horses are SO much money so be prepared to spend money on shoes/foot trimmings (my horses need shoes, very tender-footed), food, bedding, tack, etc. They are also a huge time commitment, but I'm sure you know that as well. Good luck and I hope you find your perfect horse!