I-70 is definitely faster
But both are spectacular drives. The two roads are different in major ways west of I-25 -- east of I-25, not much difference in scenery although there's more to do on the Plains closer to US50 than I-70.
(Sorry -- I wrote this as if you were driving westbound, just reverse everything order-wise!)
From what I remember about each, I-70 is greener and is perhaps more characteristic of what people think of when they think "Rocky Mountains," at least between Denver and Glenwood Springs (west of that, it dries out a lot and the trees get thinner). I especially like the town of Georgetown and it's famous railroad "loop."
On US50, you'd follow the Arkansas River for quite a distance, and cross the state's middle high desert country around Gunnison, all punctuated by a snow-covered mountain range or two (or three). If you make a side trip to Colorado Spgs, be sure to take the drive up Pike's Peak -- you end up above tree line with a great view!
Two-lane roads in Colorado are slow-going for a couple of reasons -- steeper grades and tighter curves limit your speed, as well as slowing for the frequent town or village. If you're really in a hurry, best stick to I-70, but if you can spare a little time -- you can't beat two-lane blacktop! Bob
It will be open, but not a speed run!
Loveland Pass is kept open as much as possible, because of the haz mat truck route -- but it is likely to be a slooooowwww drive (albeit gorgeous)!
Mark
in case y'all are wondering
Other stops along my trip will include Springfield, IL (Lincoln's home and burial place), Lake Superior along the shore of Michigan's U.P., Mt. Rushmore, and Yellowstone Nat'l Park.