If you ask me, it's really not a simple as picking on over the other.
I used to be strictly an STF dude, but having tried the lot, I now have a more nuanced opinion.
I can understand that some people don't like the feel of STF, but for really hard wheels (103a/83b), I definitely think Bones are the way to go. The 101a spits don't really feel like F4's anyway, so there's not really any point to them. Besides, the STF's are definitely more durable and flatspot resistant. Flatspots on F4's will roll out nicely from wearing down, but the Bones just don't wanna flatspot in the first place, and they last forever.
As for 99a, however, I reluctantly have to give it to Spitfire. I haven't tried the 97a's yet, but I'm sure they're just more of that special goodness. Like everyone says, there's just something about the way they feel. That being said, the new 99a STF's have come pretty damn close. To anyone who didn't like the "plasticky" feel of the 103"s, I'd definitely give the 99a's a go.
To summarize, there really is only one answer: NFG / Loophole
Sidenotes:
I truly hate the vibe of Spitfire. The graphical design and logo is just shit. As a little kid, I thought that burning face was almost as cheesy as the World Industries characters. It literally put me off the entire brand for over two decades, and I still feel dumb being seen riding their wheels.
Also, let's be real here. Spitfire has always been ripping off Bones. Their wheels were garbage until they tried to copy Bones and accidentally made an arguably better urethane formula. Even most of the shapes are directly taken from Bones. But in the end, who cares.