I didn't have step bars, but I did have factory mud flaps. I removed the front valance (air dam) the first week after I bought the truck, I immediately liked the change in appearance. I removed the factory mud flaps and replaced the back ones with Rally Armor flaps, none in the front. At first, I didn't like the somewhat "flappy" look because they are a thin material and are pretty flexible, but after putting them through the paces on some washed out roads recently, I LOVE them. I went through a washout with standing, muddy water and the front tires sprayed the side of the truck, but the back mud flaps didn't let a drop of muddy water get on the rear bumper or rear side. The rear of the truck was perfectly clean. Quite impressed.
It's pretty easy washing mud off the side of your truck. It is completely different scraping globs of mud out of the underneath, concave side of your rear bumper.