Nathan, When I agreed with Jill and Kay it wasn't because I didn't think that you didn't know how to handle not breeding. I was sure you did. My point was, that for a first time buyer a gelding is more forgiving while you're learning and making mistakes. Some mares will hold the mistakes you make in the beginning against you for the rest of their lives.
As for the personality, my 2 geldings have the biggest personalities on the farm!!! My yearling mare is still coming into her own with the personality. But my 13 y.o and 2 y.o geldings have the personalities that I was looking for. So saying that a gelding doesn't have a personality is a total disservice to those geldings that do.
I have been working with horses for 20+ years and I have had more geldings than mares. My geldings have always had bigger personalities, listened better, and in general behaved better than the mares. But if your friend prefers a mare then that's what he prefers. Just don't discount a gelding because he's not a mare... he (you) may find a gelding that has the qualities you wanted in a mare... Just please, DON'T TOTALLY DISCOUNT A GELDING.