We used to live in Santa Fe and have driven most of these roads frequently, although not so often with the RV. Also, this summer, with the RV, we've been all over this part of the world and have driven from Santa Fe to Farmington, to Cortez, to Moab and back again. :
Unless you really don't want to go through northern NM, going through Gallup adds at least 3 hours to the trip. You also have to take into consideration the possibility of hitting rush hour going through Albuquerque. Unless you're there before 8 a.m. you will spend at least an extra half-3/4 hour on 25 north of Albuquerque until you hit the I-40 intersection. The last time we were by there, also, there was construction west of Albuquerque on I-40 that slowed things down considerably (and was not fun with the RV -- the lanes are narrow and winding). That may have been finished by now (it was a couple of months ago) but they've been doing construction somewhere on I-40 between Albuquerque and Gallup as long as I've been driving it -- over 10 years! :
It's much more efficient to go north on 285 from Santa Fe, take 84(it splits from 285 at Espanola) to Pagosa Springs CO, where you pick up 160 as suggested, or get onto 64 (I think iit splits off at Chama -- somewhere north of Tierra Amarilla, anyway) and go west through Farmington to 491(at Cortez). 491 dead-ends into 191 south of Moab. Only one warning, that applies to every route: Mountain Directory West says "South of Moab, US 191 includes many climbs and descents that are either short and fairly steep or long and fairly mild. About 14 miles south of Blanding there is a short hill known locally as "Driveshaft Hill". It is only about 1/2 mile long but very steep -- about 11%. . .It is a northbound climb, southbound descent." If you take 491, you hit 191 north of this steep hill. By the way, we've taken this road southbound and it's not nearly as bad as I expected.
As you can see, there are a number of alternatives, but the longest by far is going through Gallup, IMHO.
Margaret