I have had both, there have been way more mares in my family (until recently I was the only one that'd ever had a gelding). Personally I shop for a horse not a gender. I love both.
That said I am always amazed at the mare bashing, I have found geldings to be waaay more hormonal! I've had a few mares that were more 'witchy' wouldn't say that's the norm, but more so then geldings, I'm assuming by 'mareish' people are refering to how they act in heat, well very few of the mares I've owned even showed signs when they were in heat, a few would flirt w/ the geldings (but were no different when riding), one tending to be more jumpy when she was in heat. And I had a pony mare that always squealed when she came nose to nose w/ another horse, of any gender whether she was in heat or not. I've had my mare squirt in front of the geldings, she's not misbehaving, or being 'mareish' she's just following instints, and as best I can remember she's the only one I've ever had do it with a rider.
The geldings on the other hand! Throw a mare in between them and they completely lose their minds!
We recently sent our three geldings (one my dad's and two mine) to a trainer for a tune up, picked the first one up Monday and I was suprised to hear him say the same thing about geldings (there was an incident w/ one of ours and another gelding trying to get into a fight across the round pen, our boy got his butt worked off for it). He said the number one thing he gets is older hormonal geldings that people end up getting because everyone says get an older gelding, they're calmer and more willing!
That said if you feel you get along better with geldings then pass on the mare and go look at some geldings.