Bones feel more like really hard slidable rubber to me, which brings to mind this "rebound" people mention. I like that because you seem to lose less speed on imperfect surfaces, like that quarter millimeter of bounce keeps you going. f4s feel more like plastic to me, I had the 99 classic and 101 tablet. Both pretty remarkable wheels for their durability but I switched back to stf and gave the 99's to my nephew. The regular classics feel the best to me, and I always go back to them at some point too.
I think people get caught up in the "f4's are the stf killer" idea, but they are both excellent wheels.