M77man,

I've been to each state twice for elk, loved them both. First time to Idaho about 20+ years ago with rifle. Second time to Idaho about 18 years ago with bow, with a outfitter and guide. Poor excuse for an archery guide, we heard quite a few elk but never saw a hair in a week. Third and forth time 3 of us did a DIY archery hunt in NW Colorado - Flattops Wilderness area. I would go back to either area in a heartbeat if I were going with the bow again. Just that with rifle, it would be a few weeks later and when we drove to the Flattops boundry, it took us over 3 hrs to go about 10 miles on this jeep "trail" - that was in a 4WD truck and without snow. I'd sure hate to get snowed in there. I would also expect much more competition and don't want to work my but off getting to an area to find a half dozen 4-wheelers parked there and 6-8 hunters all around.

All in all, I remember Idaho being lower elevation and during the guided hunt, seemed to be lots of very thick areas - heavy underbrush. There weresome cutover area from logging.
Colorado was higher - I think we were camped at about 9000 feet on a large flat and could go either up 1500-2000 more feet or down another 1000 feet or so, all within a very short distance of camp.
I'd say the part of Colorado we were in was generally steeper and more rugged than the part of Idaho we were in the last time (just below the panhandle towards the east side of the state).
I'd say Colorado lived up to it's reputation of having more elk.
Good luck in your search.