I ride and train a lot of different horses and the one thing I never think about in terms of what they might be like or what strategies I might need to use, is their sex. I've ridden flighty mares, flighty geldings, quiet stallions, quiet mares. I've worked marey mares and aggressive geldings, silent heaters and distinerested stallions.
My main concern is always the temperament- reactive or unreactive and sensitivity- do they take a lot of pressure to motivate them to respond or only a little. Most times reactive and sensitive go together but not always. Some mares can be a bit distracted or less attentive when they are in season, but then some geldings can have days when their heads are elsewhere. I've never really understood people's preference for one or the other, though its very common. I guess my view is why limit yourself to only 50% of the horse population.