I live in the Rocky Mountains and as others have said, it can be very dangerous driving through if a storm hits. In fact, the state has passed new tire laws for all vehicles, during winter storms you either have to have snow rated tires(not all weather) or 4WD/AWD. If you get in or cause an accident during a storm, the police will check your tire tread, type of tires and verify whether you have 4WD if you don't have snow rated tires and write a costly ticket if you are non-compliant.
If you do the drive, check cotrip.org often as they will update weather/road conditions and have live traffic cams, speed averages, highway closures, etc. its a great website and resource.
If you do drive via I-70, I would suggest avoiding peak travel times between Denver and Vail...the traffic is so incredibly bad. Do not try to drive from Denver to Vail on a Friday afternoon/early evening or Saturday morning. As for driving east from Vail to Denver, I would avoid the stretch on Saturday and Sunday afternoon/evenings, delays are in the hours...just an awful stretch of highway that is heavily congested with ski/tourist traffic. Also, there is a new toll system that was activated this week between Empire and Idaho Springs eastbound only, basically a 13mile stretch. There is a toll lane that cost up to $30 during peak travel periods along with two non-toll lanes...with this change there is no shoulder so all it will take is one minor accident or car break-down to cripple that stretch of interstate. Its bad already and I fear it will only be worse now.
We just got 16 inches of snow in the past 24hrs in Grand County(Winter Park area), and more storms are projected next week, so I would anticipate winter driving conditions if doing the drive through the Rocky Mountains.
Personally, I'd take the route through Colorado but i have 4WD and good tires and drive through these conditions all the time, but it probably would make the most sense to take the southern route from Iowa even though its a bit longer route, just better odds of good road conditions. I absolutely wouldn't do the I-70 route without AWD/4WD and good tires. If you have front or rear wheel drive only, please don't take I-70 through the Rocky Mtns
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