More than Utah? You sure about that? I'm LDS myself and I'll say straight up, the biggest concentration of the flock resides in Utah, from what I've seen (you could be right, I could be wrong). Although, I will say the members in Utah are quite a different bunch. I've been to Utah on many occasions and, even being a member is tough around the Utah Mormons. You can't really avoid it up there, because theirs scattered population of the church everywhere. Not saying its horrible, but the LDS mentality is typically different in Utah. My last trip there was quite an experience. Sandy and Provo are probably places to avoid. Sandy is loaded with older, close minded members who are pretty die hard traditional, and Provo is full of BYU herds. (Many of which come from Arizona actually).
Here in Mesa, their is a ton of members, but its way more laid back and we stay out of peoples hair.
All in all, Utah is a cheaper place to live. Lots of beautiful places, and theirs more non-members than people think. Also, if you love outdoor sports like climbing (amazing climbing), mountain biking (moab), riving rafting (joes valley, moab), snowboarding, skiing, etc. Utah is amazing for literally every sport. St George, has a ton of new sport climbing areas (bomber limestone cliffs). Kanab isn't far from Joes Valley and Maple canyon (both incredible climbing areas.). Kanab is a pretty boring town from what I've seen. I'd lean towards St. George.
Major downside to Utah is the cold (unless that doesn't bother you). My uncle lives in Hyrum (just north of Logan) and he says the winters can be brutal. Then again...this is coming from an Arizona native who lives in the 120's.
Good luck with your decision.