Here are the summary of the tests I made between Shredder 12 and some of the best Blitz engines.

Shredder 12 UCI           : 2429  350 (+137,=132,- 81), 58.0 %

Rybka 3                       :  50 (+  9,= 18,- 23), 36.0 %
Naum 4                        :  50 (+ 15,= 19,- 16), 49.0 %
Stockfish 1.5.1 JA            :  50 (+ 18,= 19,- 13), 55.0 %
Rybka 2.3.2a                  :  50 (+ 20,= 21,-  9), 61.0 %
HIARCS 12.1 SP                :  50 (+ 24,= 18,-  8), 66.0 %
Shredder 11                   :  50 (+ 22,= 22,-  6), 66.0 %
Toga II 1.4.2JD               :  50 (+ 29,= 15,-  6), 73.0 %

genarated by ELOstat from Arena 2.0.1

I see that the advantage of Shredder 12 is that it has better scores against its opponents than Naum 4.
I'll now test Stockfish 1.5.1 JA!

Best regards,
Orlando