Thought that I will share my track experience with the above pads and write a few comments. All my personal experience and my humble opinion.
Performance from cold:
1. DS2500
2. 971c
Good gap...
3. Blue Stuff
Big gap...
4. R&S
Performance when hot / resistance to fade:
1. 971c
2. DS2500
Big gap...
3. Blue Stuff
Massive gap...
4. R&S (hot, hate hot... Simply give up)
Pedal feel:
1. DS2500 (solid)
2. 971c (good)
3. Blue Stuff (spongy)
4. R&S (truly awful)
Progresiveness:
1. 971c / DS2500
Great gap...
3. Blue Stuff
Even bigger gap...
4. R&S
Consistency:
1. 971c / DS2500
Great gap...
3. Blue Stuff
4. R&S
Confidence:
1. 971c
2. DS2500
Great gap...
3. Blue Stuff
4. R&S
Life span:
1. DS2500 (minimal wear after 100 miles at Snetterton)
2. Blue Stuff / R&S (over half worn after 130 miles at Snetterton)
4. 971c (lasted only 130 miles at Snetterton)
IMHO, out of the 4 the best pad for everyday, fast road and occasional track use is the Ferodo DS2500 - trully versatile pad.
As for fast pure track abuse it has got to be the OMP 971c.
If you value your life then stay away from the OMP R&S track or road just avoid. Be better of going for Apec pads
Finally, as far as the Blue Stuff are concerned I will never buy them again. I will not buy any EBC stuff.
Hope this helps anyone who is looking for value for money pads.
Jack