18 or 20" wheel. Better for weight carrying and towing.

I have 20s on my Duramax and the spare is 18 witch are the same height, The 18s have a higher pay load and a better range of tire tread. The 18 inch spare has the higher load range. i wished my truck had 18 inch tire and rims. I believe the 20s are designed to track and ride better then the 18s.try a google search on 20s I found them to be miserable for 265/60/20.