Monarch Pass vs Vail/Eisenhower

For I-70, Vail Pass and the Johnson/Eisenhower Tunnels are not the only concern. Once you descend from the tunnels to the Georgetown area, it's relatively mundane driving, reasonably flat through Idaho Springs. East of Idaho Springs you have the Floyd Hill climb, which, even though guides say it's the same incline as Vail and the tunnels, just always seems steeper to me. And it's a goodly climb to the top. Then, as you approach Denver, you have a long descent to the outskirts of Golden and the intersection with CO 470, which is what I would recommend if you're going to Colorado Springs. There is no reason to go into Denver proper (unless you have a need/desire to go to Denver) when CO 470 will take you around to I-25 south of Denver.

There are other alternatives, such as getting off I-70 east of Eagle on to US 24 and taking that up to Leadville, then continuing down through Buena Vista/Johnson Village, then east on US 285/24 to US 24 through Woodland Park and on down to Colorado Springs.

That said, I would also recommend US 50 up and over Monarch Pass. I just find it a more enjoyable drive.