We are in MA right on the NH border and are actually planning the same trip. However we have added in stopping at Glacier NP. My vote is to definitely take the motorhome. It may be a little more expensive but the experience will be worth it. Our trip out includes stops at Niagara Falls, Badlands NP, Mount Rushmore, Crazy Horse, Devils Tower, Glacier, Yellowstone, Grand Tetons. And when we start coming home we will are going to hit Dinosaur NP, Canyonlands NP, Arches NP, Mesa Verde, and Sand Dunes NP. Right now we are planning 4-5 weeks or so. There is so much to see. I can't imagine not camping when going cross country.