Performance is such a subjective thing, hard to quantify. I have enjoyed the pleasures of one of TER's top ten providers, who, by any standards is an absolute tops in performance: She loves role play, toys, greek, cim, ropes, lingerie, well, you name it, she is simply a sexual dynamo and an expert in the art of courtesanship. So, using her as a standard of comparison, I'd have to concede that many of the younger SBs I date are nowhere near that level. Some have limited menus, even for what we'd consider vanilla activities, ie, no sex in the doggy position, or no oral!
Otoh, some are simply sexual dynamos themselves, completely uninhibited, capable of multiple O's, open to any activity I may suggest and full of suggestions on their own. So It really varies, even within the limited age group I favor.
And finally, there's the unknown factor of what turns you on. I say unknown, because you never know until you are actually in bed with someone how you are going to respond. I have one SB in my rotation who affects me profoundly for reasons I cannot explain. She's young, 19 just about to turn 20. She's very pretty, but so are many of the girls I date. And she's not a particularly skilled or sophisticated performer. But to my own astonishment, the first time we had sex I actually came in the condom while screwing her, something I had not been able to manage in 20 years. There's just something magical about the way she turns me on and makes me climax. It has continued this way every time I've visited her, and it doesn't happen for me with anyone else! It's a complete, but delightful, mystery. So is she a top performer? Maybe for anyone else she'd just be average. For me, she's amazing and I'll be visiting her again in 2 days. Can't wait to see if she affects me again the same way!