Correct me if i'm wrong but i think that the PCR also has pivot ball suspension,c-hub goes on the hyper 7 and hyper 7 pro.
Check this out:

http://www.ofna.com/matrix.html

And i think the pivot ball suspension has stronger "moving parts" and bigger which can take more abuse,although on a race they get dirt insite and can "bite" on the suspension and steering!
That's why the c-hub is better for racing(correct me here...!!!)[&:]