Your weight and weight on the bicycle. If you weigh 150lbs pretty much any rim appropriate for the size of tire in 32 hole rim. If you weigh 250lbs carrying 50lbs and wider tire I'd go for a beefier wider rim in 36 spokes. Rhynolite or Velocity Cliffhanger. If you're in between there's a huge range of 22mm to 25mm wide rims available.