Yes I know that they have used the basic design for many generations of the 2wd line,but I have found them to be durable,yes I agree that they should get rid of the offset ballcups but the rest seems to work very well,at least in my experience with them,I agree that the xb2 is nearly bulletproof!!thats why I used the dirt edition gearbox etc on my hybrid car. As for the other brands I have no experience with them.
Cheers