Painted Horse offers good advice. I'll toss in a few other things to consider... If you're going with boots, the Boa are probably a better option than the Easyboot. The Boas have substantial traction incorporated into the design, while the Easyboots will need to have traction added, and as the photos Painted Horse included indicate, you'll want good traction!!
If you're going barefoot, the SoleGuard is a good idea. Personally, I wouldn't go the barefoot route if I were you, primarily because you're going from the "Midwet" to the dry West. While the rocks may not be different, acclimating a hoof to such an environmental change takes time. Your horses' hooves will be heavily hydrated in comparison to those native to the area. Subsequently, they're just not going to be as tough.
If you're going with shoes, I would suggest a borium surfacing material be applied. In general, steel shoes will provide less traction than a bare foot, and a little traction might not be bad (again, check those photos!). I'm not a fan of adding traction, but it's better than falling down!
The only time I've every had traction problems is when crossing large sheets of granite. Steel and granite just don't grip to each other. (Aluminum and granite really grab hold of each other) But large sheets of granite are the exception. Most trails are on broken piece of rock, Cobble and gravel with fine particles in the cracks. The horses feet seem to find purchase in the rock cracks, and between the cobble.
I've used the plain Easyboots, Easyboot Epics and now the Easyboot BARES. Friends have used the Boas. My biggest problem has never been the traction offered by the different boots. But rather breaking the fastning system. The buttons break off the boas, The buckles and cables break off the Epics. I have found the Bares the most resistant to breaking, since there is no exposed fastner.
We took 11 horses in one weekend with boots on the front of all. 10 miles later we had broken the buckles on 19 of the 22 boots.
We've used cotter pins, we've wrapped the buckles with duct tape. It just doesn't matter when you get in the rough stuff, the horses will drag the boots across rocks, stumps who knows what, But you end up with what ever is on the front of the boot being broke. Where as if you ride down a nice gravel road, smooth trail, sandy arena, they never break the buckles.
You cross a stream, their feet get wedged in between boulders.
If you leave the trail at all and have to cross blow downs, they bump the logs with the boots.
The horses quickly learn where to put their feet, They pick their way through the boulders and do a good job of finding a path. Here it was so rough we got off and lead the horses through a boulder field.
Often times the trails are made of rocks. Notice the boots on the front feet. Back hooves were barefoot.
If you put shoes on, Make sure they are in good shape and tight before heading out. Horses feet getting wedged between rocks will pull shoes off. Especially if the nails are loose or worn. Plain steel shoes do very well in sandstone or shale like we have here in Utah. No Borium needed.