I have had two mares and love them dearly. I have a gelding and mare now
and am possibly about to get another gelding, but I would get a mare
for myself any day (this gelding is for the kids). With regard to heat cycles,
mares differ, but there are herbal products on the market to help soothe the
cycle.
I think it mostly depends on the horse, not the gender, although some
people say they don't get along with one or the other.
