I lived in Seattle for 4 years (2014-2017) and moved to SF in 2017.
1. Over time the weather in Seattle got to me and I became depressed. I've gotten more sunshine in the Bay Area and that has made all of the difference to me. People complain about the fog in SF but after living in Seattle and Portland I find SF weather to be almost perfect year round. The things I don't like about SF are well documented in the news and social media, just look it up on YouTube or Twitter and you'll see footage from Market St. / Tenderloin areas.
However, most of my time is spent between Golden Gate Park and the Presidio, which is just beautiful and pretty chill. The neighborhoods are walkable, have natural beauty, great food, and various venues where I enjoy hanging. So while I often see SF described as a "hellscape" and a "warzone", much of my daily life feels like a pretty postcard and is fairly quiet and peaceful.
2. I owned a 3 bedroom townhouse in Seattle but rent a 2 bedroom flat in San Francisco. I saved a lot in taxes and had a low mortgage in Seattle. SF is definitely more expensive, but the added cost was worth it for me since I've personally been happier. YMMV, some people seem to hate it here.
3. My pay went up in SF and I have had a variety of opportunities that I might not have had elsewhere.
4. Yes, I have been better at making friends in San Francisco. I never had much of a social circle in Seattle and failed in my efforts there. I do feel like SF has become a bit worse socially since the pandemic. I made quite a few new friends pre-2020, but not as many since. Also some of my favorite music venues and hangouts closed down in recently years.
5. I don't know anything about schools, day care, etc.