Most of the time the tunnel would probably be a better bet. From the west portal of the tunnel its 8 miles down to exit 205 then about 6 up to Keystone. You always run the risk of getting caught behind HC trucks on the pass with very few passing opportunities
On the other hand if time is not an object-enjoy the views off the pass.
I disagree. Unless you're stuck behind a large tractor trailer, I think Loveland Pass is much quicker. Especially on the way home- everyone and their brother goes on I-70 and the traffic coming up to the tunnel can be horrendous, specifically when there's bad weather. I take the pass every time if the roads are in decent shape.
I lived in Summit Cove for 3 years. It's almost exactly equal as far as time goes. Mostly it depends on which liquor store you stop at for beer on the way. I think Bob's in Silverthorne is quicker than stopping off at Keystone. Coming from Denver I'd just suggest Applejacks.
I decided to try both today, went up through the tunnel and down through the pass. Didn't notice a big difference in time. Will probably do the same next time as long as it's not snow packed on the pass, and by the way it was a beautiful day at Keystone.