Highway US14A is VERY STEEP and winding west of Sheridan. Highway US14 only marginally better. Both are scenic. If you are an experienced RV mountian driver, you won't have problems. If you are not you might find the road intimidating.
I personally find US16 from Buffalo, WY to Worland a much preferable drive. I like to stop in Thermopolis and soak in a hot spring on the way through.
You will find that if you are coming from the east the distance is about the same regardless of the route you choose.