ACR X TCASII RA HAD LTSS FROM ACR Y SYS ERROR. EVASIVE ACTION TAKEN.

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ACR X 737 WAS HOLDING 340 DEGS; CLBING TO 17000 FT. INSTRUCTED TO 'EXPEDITE THROUGH 12000 FT.' ACR X B757 DEPARTED 8 MI SW OF THE B737 HDG 345 DEGS; CLBING TO 10000 FT. THE B757 WAS TURNED TO HDG 260 DEGS 4 MI N OF THE ARPT. AT APPROX 7000 FT THE B737 ADVISED THAT HE WAS RESPONDING TO AN RA AND DSNDING. THE B737 WAS FILED AS A 300 SERIES BUT FAILED BY FAR TO MEET MY EXPECTATIONS OF AN EXPEDITIOUS CLB. THE 737 WAS EITHER VERY HVY OR NOT REALLY A 300. THE B757 WAS CLBING AT A VERY HIGH RATE; POSSIBLY AFFECTING HIS RATE OF TURN ALSO. AT THE POINT OF THE RA; A B737-300 WOULD NORMALLY BE ABOVE 11000 FT. I FAILED TO RECOGNIZE THIS DISCREPANCY. CTLRS PLACE A GREAT DEAL OF IMPORTANCE ON ACFT TYPE. MANY TIMES A CLB WILL BE ISSUED TO A B737-300 OR B757 THAT WOULD NOT BE GIVEN TO A B727 OR DC9. I'VE RARELY HEARD AN ACFT ASKED WHAT HIS RATE OF CLB WILL BE; BUT THROUGH EXPERIENCE; CTLRS KNOW WHAT TO EXPECT. ANY TIME CIRCUMSTANCES EXIST THAT PREVENT AN ACFT FROM PERFORMING NORMALLY THE PLT SHOULD BE PREPARED TO ADVISE; PARTICULARLY WHEN INSTRUCTED TO 'EXPEDITE.' IF THE PLT HAD SAID 'WE'LL EXPEDITE BUT WE'RE A DASH 200 TODAY (AS IS OFTEN HEARD) THIS MAY HAVE BEEN PREVENTED. EQUALLY; IF I HAD BEEN MORE ATTENTIVE TO ACTUAL PERFORMANCE INSTEAD OF RELYING ON WHAT ALWAYS WORKED IN THE PAST; NO CORRECTIVE ACTION WOULD HAVE BEEN REQUIRED.