For me, it breaks down like this. For anything I've been away from for a while, the simpler sites work better. If I've been back involved (so I'm not asking simple questions), SO is the way to go. I'm ok with this.
I really dislike the fact that I can't distinguish in my search results between good SO results and bad SO results. So many times I'll click their result only to go to a page that has been 'closed because ...'
Sometimes I can still see the answer there (someone will have answered before it was closed), but often SO is a huge time-waster for simple things.
I find W3Schools to be the fastest solution for figuring out why my 'font-decoration' css style isn't working (like I had to do yesterday).