My last two dogs I've had were rescues and were nuetered as all rescues here are.

My dog Harry (Pit mix) is almost 9 now, is fit, trim, alert and obidient like a soldier. Dogs that eat too much and dont get excersize, like people, gain weight, nuetered or not.

If you are not breeding I would say snip him.

I would also ask dog trainers(vets may be partial) what they see in behavioral differences and their opinion. They should have a wide variety of experiences and preference.