It also depends on the horse breed. Like I have 2 Arab mares that I just love and they are fantastic horses. And I have 2 geldings as well that are Quarters horse and Appy. All horses can have an attitude. Geldings are stereotypical more laid back and not as hard to work with as mares because of their hormones. And mares do have a stereotypical time of being more hormonal. Trail riding I haven't had a problem from either type, they are both wonderful. My Arab will really put her trust in me and do things that I ask her to do even though she might be a little scared.
And just on a side note, my dad loves mares because you can breed them. All the time and work you put into one you can breed and carry on traits of the horse. A gelding you can not do that. Just a point. LOL.