I have fussed with various cameras, and scopes, for guiding. My emperical observations boil down to this. It's about exposure time on the webcams, and the orion SSAG is just a souped up webcam with long exposure capability. Traditional webcams wont go much beyond 0.2 sec for exposure time.
I've done measurements in my ST80, and this is essentially the result, all measurements done in my short tube 80 on the eq6.
NexImage (philips webcam) using 0.2 second exposures allows guiding on a star down to about mag 7.5 reliably.
Orion SSAG running at 0.2 second exposure allows guiding on a star down to about mag 7.5.
Orion SSAG running at 1.0 second exposure allows guiding on a star down to about mag 10.7.
Orion SSAG running at 2.0 seconds of exposure allows guiding on a star down to about mag 11.2.