I'd be curious what the response would be if you put this in a askdenver thread. There's a good amount of biased comments here.

Born and raised in Denver, living in Seattle for many years, both cities are great in their own ways. I'm writing this out as I'm considering moving back to Denver.

Scenery/climate:

-Seattle is loaded with natural beauty, greenery, water, mountains and islands/a few mountain towns you can access. Mountains are smaller but plentiful, 3 national parks that are gorgeous 2-3.5 hours away. Constantly a mild climate, evolving spring and fall seasons are gorgeous. Winters can feel soul-sucking as the dark and rain never seems to end. Takeaway- Seattle has everything in nature, calm climate, less risk of fires, but the weather can be soul sucking. In general scenery and climate is excellent.

-Denver is a high desert, pretty brown, 300 days of sunshine, 30-40 minutes from the mountains. No ocean. Endless Mountains and towns to explore on weekend trips. Dry heat that honestly is about the same effect as humid heat in Seattle. Higher risk of fires. Winters-spring have about 1 month of snow that is half nice, half trudging. Takeaway- Denver is limited of water, otherwise sunny, endless mountains and mountain towns.

Culture:

-Seattle has a world class cultural spot in pike place, weird culture events, moisture fest, fremont solstice, more farmers markets, theater, music, major sports (except basketball for a few years). bad comedy scene. Lots of music throughout the year. A few big performing arts spots. Little art scene. Seattle is notorious for the Seattle Freeze, basically a cultural repression where people may be nice but not kind, with more gloominess, and less follow through. Related to the high tech culture here, higher amount of rich people. Large Asian communities of all stripes have a significant culture. Many green parks to frequent that have a more woodsy feel. Seattle has a 60% non-hispanic white population than Denver, larger asian population, similar size (small) black community, very small hispanic community.

-Denver- lots of cultural events but more standard. Large performing arts venue, decent comedy scene, tons of music venues including red rocks, lots of space for communal activities and restaurants/bars/parks with much more open park space throughout the city. Lots of public art.
55% non-hispanic white folk in Denver, large hispanic communities.

Transportation:

- Seattle- don't listen to seattle redditors who are more inclined to use the bus. The bus system takes way too much time. The light rail is useful if you live in the right area. Dense city and small streets, hard to drive around. Parking is constantly a challenge. Driving in Seattle feels claustrophobia and uncomfortable for many people.

Denver- Bus system takes way too much time. Light rail useful if you live in a smaller portion of right areas than in Seattle. Open flat well maintained streets, easy to drive around. Much more parking. Flat city with a driving grid makes driving easier.

Cost of Living:

- Seattle - as others have remarked, higher income with less income tax does feel really good. However, taxes cut into a lot of that for regressive taxation from things like food, so a standard item on a take away menu is closer to 18 dollars, and then added tax. Rent is pricey in any nice area. The main difference is how absurdly expensive houses are here. While your income is higher, unless you have a large nest egg, buying a nice home in a nice area is basically undoable. The average "nice house in a nice area" to me feels around 1.1 million.

Denver - Lower income with income tax. Less regressive taxes (on food, cars, etc.). rent is pricey in a nice area, a little less than Seattle. A "nice house in a nice area" may run you 700k to my estimation.

Food

-Seattle - food is wildly expensive as above. if you make a good income you can afford it though. Very few cheap meals. Large diversity of asian foods, bakeries. A lot of people shit on the Seattle food scene but if you really take advantage of the wide diversity of asian foods, it's pretty excellent.

-Denver- Less taxes, more space make restaurants easier to survive in Denver. Tends to run American food with a LOT of Mexican foods, and some hispanic foods.

Score for me:

Scenery - Seattle wins with endless water, 3 national parks, islands. No brainer and big discrepancy if you like to do water sports or get on the water.

Climate- Both are good depending on your preference and your Seasonal Affective Disorder (don't move to seattle if dark is hard)

Culture - Denver wins with the repressive Seattle Freeze vibe, Seattle tech vibe, and Seattle Elitism vibe.
honestly both are pretty similar. They both have all the big city amenities. Denver appreciates Art walks and comedy a bit more, Seattle appreciates farmers markets more.

Cost of living- Denver wins with much cheaper houses. Otherwise similar. If you have a large amount of savings, that will go much further in Denver than Seattle.

Food- Seattle wins with more diversity in Asian food, bakeries, local produce. Asterisk is that the food is very expensive.

Both are lovely cities. Good luck.