I would say that my current brakes are similar to what Jim describes above. Maybe 90% of the Girlings.
Based upon what I have experienced in the past Girlings are better as they are dual piston (one each side) vs single piston - static one side as modern brakes often are along with a bit more contact area on rotor.
The PBR type are used on typical 4000 cars etc... No quality issues, no doubt $$ factor
Girlings will set you back a couple dollars, generally not for weak knee's.
KMS uses Wilwood STD, Girling optional I think which are again improved over PBR type and work like manual brakes do.
To be honest, solid rotors do not move heat as well as vented. In racing conditions nothing is perfect and wear a violent competitor. Racing = brutal on wear items.
Why the change?
If you ask that you don't know me.....
I did have the option of Girling steel calipers, just went for the race. (I'll add a picture later)
I'll post pics once I assemble, the Magnesium wheels are 6.5" and also cast a little different than alloy. We will see together....
Below is Jim F car, set up by Cobra Automotive.