Thoms route is the way to stay in the mountains of Colorado. The drive up the Crystal is beautiful. (In fact, if you're staying around Carbondale, it's worth a day trip up to Marble just to explore this area at leisure. Keep an eye out for Hayes Creek falls on the west side of the highway and do make the loop into Redstone.) Once you get past the Marble turnoff, the climb to McClure Pass is steep (8%) but only three miles long. The decent is generally gentle, but use your gears rather than your brakes.
On the other hand, if you haven't been through red rock county, your route is a good way to get a quick look at it on the way through. I would note in your description, you need to turn off of US 191 onto US 491 at Monticello to get down to the turn for CO 184. Don't miss the jog in the road just past the Anasazi Heritage center before Dolores. Left on CO CO 145, right on CO 184 a mile later. CO 184 winds through pretty farm land, while US 160 between Mancos and Cortez is more arid.
Either route works fine. Do you want mountains or red rocks as your main scenic attraction for the day?