Which conceivable method of summing is the least problematic? Depending on the summing method you might find yourself advocating creating as many people as possible with positive utility, or eliminate everyone with below-average utility, etc.
Utility is very complicated and summing might not even be possible. Folks have argued for completely different utility systems, such as cardinal utility where utility is modeled purely as relations instead of something that is isomorphic to a real. Even going by the mainstream view of ordinal utility, utility tends to be a convex function (simplistically, having 1 food is much better than having no food, but having 1000 food isn't that much better than having 500 food.) Modeling utility as something purely isomorphic to reals gives it all the fun paradoxes that we know the reals have and can be used to create some really wacky results. The "repugnant conclusion" is a direct consequence of that.
