When I switched from HPI Pro4 to XRay T2 I noticed a big differance.
Even over time the Pro4 had more and more slop. I constantly tried to reduce slop on it. All joints would loosen up over time. I think the plate that controls ackerman was the worst. The car has a lot of links connecting the steering overall.
With the T2 slop has been at a minimal. Only the servo horn and the steering knuckles tend to come loose from time to time. Less links, especially at servo saver.
Hope this helps.