I believe the HS81's are some of the fastest micro servos available in their size range. I was comparing them with JR servos a while back and I distinctly remember the JR ones being slower, which surprised me.

I may be wrong though. Using JR servos because you have a JR radio won't make much of a difference in anything anyways. Servos are only motors and gears, nothing more.

I'd stick with the Hitec servos if I was you, but that's just my opinion . I assume you're asking because you've stripped the nylon gears in your HS81's on crashes? It's a common problem, but metal gears strip too, and a hard crash will likely strip even the metal gears, so i'd be careful with going the metal route unless you're sure you can avoid crashing alltogether, otherwise you may only be wasting more money than you need to .