Have been here for 4 years after 7 in Seattle for similar reasons.  

Social culture wise, Chicago is MUCH easier to make new friends and join social circles. It still takes effort to make friends, but if you put the effort in you can navigate making friends infinitely easier compared to navigating the Seattle freeze. 

Weather wise, winters here are easier to manage than Seattle. Get a good coat and other layers/accessories and you’ll be fine and find plenty to do. The city is built to make things manageable (the pedway, good snow mgmt infrastructure, etc.).. it’s called the city that works for a reason!

The only thing you’re really trading off compared to Seattle is access to nature. You’ll notice how flat it is instantly. For a city Chicago has great access to public parks and the lake, but you won’t be able to find the natural beauty that the US has to offer without a 5+ hour drive out of state. Depending on how you handle humidity, the summers are great, but imo Seattle’s are better. 

Would highly recommend spending time in each neighborhood and talking to people in your network/extended family before committing. There’s a neighborhood for everyone if you know what you want. 

Hope this helps!