I subscribe to Baseball Prospectus, but mainly for the "Under the Knife" feature and their PECOTA projections. Most of the other stuff is crap.
I know a guy in my main league who uses HQ, and he swears by them, but, again, I think it is the projections, not the articles (and while he does OK, he isn't competitive every year). At $99/year, no thanks, especially since the base concepts are explained for $20 in their yearly book - and you can then determine who they like from that and then applying their concepts to your league.
A couple others in the league use Baseball Notebook, but for projections only since I think all of their articles are free.
Now, I am an ESPN Insider for the Rumors and articles not related to fantasy baseball. In fact, I don't even bother with Tristan Cockcroft. He was a joke at CBS and he is now an "expert" at ESPN. Whatever. I honestly would love to know who he has photos of because I (as well as others on this site) could do a better job of fantasy analysis than he does. Anyway, while Karabell is decent, I think his blog his free anyway. At least he sems to understand the nuances of fantasy and that there are different types of fantasy leagues.
Otherwise, that's my $0.02. In summary, from my experience. Madison is right - unless you are looking for fantasy projections, I don't think there's any pay site I would pay for just to get the articles. Most of these sites were not pay-only from the beginning and unless things have changed, they all seemed to recycle the same stuff. They'll all tell you things like "Hermida is a top rookie" and they all seem to have the same list of "sleepers" - which means none of them are in my league. So, save your money would be my recommendation.