difference between the bart 8s and 8st?

FWIW:

headed for the backburner and no response so I'll throw out my 2 cents.

I've had two Bart P's and they sounded the same so I'm guessing they were both 8S - not marked so who knows.

At any rate, I'd say that description gives you a ballpark idea. If you've played enough different P's you're better able to fill in what's missing. No way to nail it cause of other variables - I'd predict the acoustic properties of a dark vs bright bass would have at least as much impact as the variation of the deep and brighter version of the pup but I don't know that for a fact.

Also, depending on what tone you're after, you'd want the pup tone to balance the acoustic properties of the bass, typically a darker pup in a brighter bass and vice versa.