DASH 8 ACFT HAS DIFFICULTY WITH ATC VECTORS DUE TO PROB OF DRIFT-DOWN AND DIVERTING FROM FILED ROUTING.

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WE HAVE DRIFT-DOWN PROCS WHICH INVOLVE STAYING ON FILED ROUTING. CTLR WANTED US TO GO DIRECT BLUE MESA VOR; WE SAID WE NEED TO STAY ON OUR FILED ROUTING FOR DRIFT-DOWN. (ROCKIES 2 DEP BLUE MESA TRANSITION) HE SEEMED SOMEWHAT AGITATED AND TOLD US WE NEEDED TO GO EITHER R OR L -- OUR CHOICE. WE DECIDED ON L TURN -- WE WERE ABOUT 30 DEGS OFF COURSE. HE EVENTUALLY PUT US BACK ON OUR FILED ROUTING. HE HANDED US OFF TO ANOTHER SECTOR AND THIS SECTOR TOLD US TO CONTACT CTR WHEN WE LAND. ZDV CTLR'S HAVE BEEN ADVISED OF OUR SIT WITH DRIFT-DOWN. HOWEVER; SOME ARE ANNOYED BY OUR INSISTENCE TO STAY ON COURSE. OUR SIT IS THAT WE CANNOT DEVIATE MORE THAN 5 MI OFF COURSE TO INSURE TERRAIN SEPARATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ACFT WAS A DASH 8 AND IT DOES HAVE POOR SINGLE ENG CAPABILITY AND IS NOT A GOOD ACFT FOR THIS HIGH ALT OP. IN FACT THE COMPANY IS GETTING RID OF THESE ACFT. RPTR WAS NOT THE ONLY PLT WHO HAD DIFFICULTY WITH ATC REGARDING THE COMPANY POLICIES. COMPANY HAS REVIEWED PROCS WITH ATC AND HAS MADE THE REQUIREMENTS MORE LENIENT SO THE FLC CAN JUDGE HOW FAR OFF COURSE THEY FEEL IS APPROPRIATE. MEA IN THIS AREA IS 16300 FT WHICH IS VERY HIGH FOR THIS ACFT.