I'm a Mare guy and prefer mares over geldings. IMO, they seem to bond better with you, much smarter and fast learners, eager to please, I just find I get along with mares better. IDK, why I just do. Matter a fact I have zero issue with any mare in our barn. Even when they go in heat where folks say they get moody/temperamental and/or can be a handful to control. I don't have these issue at all with any of my three girls. Matter a fact Babe and Mea really don't show and signs there in heat. they just get more friendlier. Gypsy easy to tell cause she gets really "flirty" with me when she's in heat.(she's confused and has no interest in any gelding in our barn) She does get a little nippy with me(playful nipping, doesn't hurt) It's not an issue so I don't correct her cause she's just being a horse. She just does it to me no one else nor other horses so I just let her be. I just say "Gypsy you're a weird-o! LOL!" I've been out on trails and camping when there in heat and no issues, she don't have interest in horses. I guess it all depends on the horse, much like people they have different personalities.
My girls do get jealous over one another(except Mea) mainly Gypsy and Babe both want my attention. That one thing I noticed with my mares is jealousy and did not notice Geldings getting jealous with there owners when they paid attention to another horse. the males seems to just go on about their business. That's the only issue I have with the girls, they are best friends out in the field when I'm away. but... when I'm at the barn I can't let them roam the barn together. Even when I got hang with them in the field. It's Gypsy only cause she wont let any horse come near me. (Never use to do that, when I first got her) That's the only problem if you can even call it that.
I always tell people looking for a horse and tossed up between a Mare or Gelding is spend time with the horse. That's the only way to see what they are like. (Sorry for the long post, I know I can ramble on when it comes to horses, cause I;m such a horse nut!)