Had 17" wheels where the over all diameter of the tire was 29.5" tall...(after going to bigger wheels/tires also installed Kore race suspension... wash board was like a paved highway after that) went to 20" wheel and a 33.4" tall tire on my 05 3500 Ram, ride difference? never noticed... what I gained was longer rotor and caliper life as the snow and mud didn't pack in any where near how it did with the 17" wheels, where the mud would pack in and not allow the caliper the release when the brake pedal was released. the larger wheels have larger "spokes" easier to expel mud/snow and not to mention easier to clean at the truck wash!
Be fashionable... go with the 20s... :B