
First off, it's not really you (as the dog owner) that decide to use a dog at stud or not -stud dog owners are approached by bitch owners that have seen your dog do well in the show ring. :) Advertising dogs as available for stud isn't the done thing with responsible breeders, and so if you did that, you'd only be approached by the wrong kind of people. (Like those breeding to make money.) I.e. even if your dog turns out to be healthy and good looking, he may still not be used at stud, or you may be asked -there's no way of knowing.
I have 3 entire male dogs and 4 neutered dogs. There is NO difference between them at all. They all do the same things. The neutered ones even mate and tie with bitches in season given half a chance. My oldest entire dog is 12 ½ years old and he's not a stud dog and never has been. (He did sire an accidental litter which was entirely my own stupid fault, and I lerant that lesson.) My only reason for having neutered some are that they were never going to be shown and it makes life easier for me as there are less entire dogs to worry about when I have a bitch in season. :)