I’ve hunted in both. One isn’t any better or easier than the other, just trade-offs.
My advice - Pick the one that is closer to where you live and go hunt. If you can save 7 hours of driving then that gives you an extra day of hunting.
You will learn a bunch either way, but ideally you want a place you can return to every year that you don’t draw a LE Tag. It will take you a while, but having experience in a unit will increase your chances of success every year.
Both states have good OTC units but neither are easy OTC. Idaho has a Wolf problem and Colorado has a bunch of hunters problem. It's kind of a wash. I've hunted each OTC and I prefer Idaho.
If you are not interested in spending the first day or so doing just about nothing but drinking your weight in water, you are likely to have altitude issues that you do not want for a second.
I've hunted both . Idaho is a little cheaper for out of state tags. and found it a little more rugged. Colorado is a bit more pricy . But have to say , for seeing elk I would have to say Colorado. Have been into elk mostly every day I have hunted Colorado . Idaho has a lot of ATV traffic . Not a fan of that . Hope this helps . Once I get to the PM status on this site , definitely PM me.
Your odds are going to be near the same in each, pick the one that is closest to you in terms of drive time and go. (Yes I’ve hunted both)
Most folks think if they find the magic state/unit/escouting spot they’ll get an elk. Exact wrong way to think about it. It’s 100% about how much you know, how much you work, and where you go on a “micro” level. Spending an extra day somewhere because you’re not driving farther to some “greener pasture” will give you the most important thing, more experience in the mountains.
As an example, I shot an elk within 3 days each time I went to Colorado. But I switched to Idaho because it’s closer. Not concerned