Stallion OR Gelding . . .?

It depends on what you want to do with him. If you want him up for stud, then obviously, don't geld him. If you want to show him really prestigiously, then it may be against the rules to have a gelding. But if you are showing locally, or just riding for fun, then it would be a better idea to geld him so that he is calmer and gets along with the other horses better.