With mapping in general, lat/long is a more "universal" system for the globe as whole, while UTM is better suited to smaller geographic areas (like those at which we use to hike!) The series of 60 UTM zones across the globe all reduce distortion at localized (regional) areas, but if you were to use UTM coordinates in, say, polar regions you'd get some distortion/error as compared to lat/long...you can see this effect on a wall map where Greenland and Antarctica look enormous. Many of those maps are in some form of the Mercator projection. Since we don't often hike in polar regions, this isn't an issue for us
You should also be aware that distortion increases a little when you're near UTM zone boundaries, so it's a good idea to know which UTM Zone you're in, as well as if you're near a zone boundary. I believe that most GPS units take this into account. Here in central Arizona, we're in UTM Zone 12, but the west part of the state gets into Zone 11.
I realize it's a long-winded answer, but UTM is perfectly fine for hiking at these latitudes, as is lat/long. It's just good to know both systems. The units of meters versus degrees, though, is why I find it easier to convey hiking distances in UTM, as big_load said. Now if you want to get away from metric, you can use the State Plane Coordinate System to get to feet, but that's another conversation ;)