Denver has gotten a bit expensive to live but I think it is still a bit more affordable to live there than Bellingham especially if you get a place in the suburbs.
If you get up early you can beat most of the ski traffic but most folks do plan for a 2-4 hour drive each way depending on location. I live an hour South of Denver and plan on a 3.5 hour drive each way which has impacted my desire and ability to ride this reason.....just not been very motivated this winter to get out despite the many invites I have received to sled (thank you to all who were willing to take this unskilled rider along with you this winter).
I'm biased but would recommend the Denver area for year round opportunities.
Sledding is not a passion of mine but a means to kill time during the winter months. I live for Colorado summer months that we use to camp/ATV/hike/explore as much as possible. I cannot wait for the snow to clear up so we can ATV and camp again.
If you like to offroad with a Jeep then I can't think of a better area to live.. There are so many areas to explore and I have yet to take a vacation outside of Colorado in 10+ years.
Not sure of the singles scene in Washington, but my single friends and relatives don't seem to care much for Denver women. Many say the young ones are very materialistic and care more about your salary than you as a person. The ones who don't care, i.e. outdoor type gals that I prefer, seem to be die-hard tree hugger types which isn't compatible with my powersport activities and belief system. I'm fortunate in that my wife, a Denver born native that I met while stationed in Alabama, is my perfect mate. She likes the outdoors and unlike most "granolas here who do too" shaves her legs and pits
and doesn't wear flip-flop sandals year round.
Good luck in your choice and please tell us where you decide to go and keep us posted about your future experiences.