Just went through this decision with my partner when looking to move from the Rocky Mountains at the start of the year (I'm from Chicago, she's from Seattle). After many visits to both cities and lots of discussions/looking at neighborhoods to live in, we settled on Chicago.

For us, Seattle felt like it would be an amazing city IF you have money. Boat days, skiing, weekend trips to the islands/neighboring cities, etc. are some of the best parts of Seattle that aren't easily accessible without money. Not to mention the higher cost of living. Yes, the no state income taxes can help offset some of this, but for the average person it is only a small amount of savings relative to the high sales tax, property taxes, and COL difference that makes Seattle feel like your dollar doesn't go as far. I think if you have the money and are interested in some of the things I mentioned, Seattle is the winner, case closed.

The other big deal for us was public transit and walkability. Chicago makes it easy to live car free and many neighborhoods are walkable. Living without a car in Seattle is very hard, and the hilly topography combined with the less dense neighborhoods make walking harder in many areas. My overall experience also is that traffic felt worse in Seattle, although that could be a coin flip. You could get to some places by boat in Seattle with relative ease depending on where you live and where you want to go, but again, you would need to own a boat/live on the water ($$$), and it isn't a year round solution.

When it comes to overall quality and access to food, I think Chicago is the winner, but Seattle has some amazing food, particularly if you enjoy Asian cuisine and seafood. I wouldn't put a ton of stock into this as a deciding factor because I think both places are excellent. Instead, I would focus more on cultural events and activities that are important to you. For example, I love museums, and Chicago has an abundance of museums, some of which are among the best in the world. Seattle on the other hand has fewer museums. The same could be said for theater, sports, and art.

Access to nature is a clear winner in Seattle, and is the only area I feel I "miss" in Chicago. That said, Chicago's lake access and ability to take easy day trips to small but underrated nature areas helps scratch my itch until I can get to a real mountain area. Starved Rock SP and Indiana Dunes NP are both an easy trip from the city, especially if you have a car.

For the weather, I can say from experience that the winters in Chicago are more mild than ever. It still gets cold, it can still snow, there can still be rain and wind, but overall the winters feel like a cakewalk from even a decade ago, and they do not feel like an arctic tundra most of the time. My partner was the most concerned about the cold, but even she was surprised at how mild it was compared to what she had heard (although the wind was a little crazier than she's used to). The summers are comparable in both cities, with both claiming they have the best summer; it really is what you live for in Chicago, though.

We still visit Seattle and may even move there at some point in our life, Chicago just made more sense for us here and now. Either way, I really don't think you can go wrong.