I have been to the midwest and while the people are a lot friendlier and polite and it is a lot cheaper to buy a home than San Diego, I am a weather freak and addicted to beach weather.
As for SF versus San Diego, I lived in SF and it was ok and fun but I prefer the more laid back beach feel to San Diego.
If I was to live in the midwest, Minnesota and Madison, WI would be good places but I am a baby and don’t do well in cold weather. But I would easily find a nice lady to date and afford a home so who knows?