I tend to do a mix of the two...I post what's on my mind at the moment but I try to either write about it in the ways that I know my readers will respond to or add something on that I know they're interested in. And then of course there are posts of mine that I do just because they're of interest to other people(don't get me wrong, I'm interested too, but I probably wouldn't have bothered it they weren't as well, often more than I am.)