As a rule, the 85 combat trigger is better than the 75b trigger because the 85c doesn't have a firing pin block. Having never shot a 75SA, I couldn't say if its trigger is better than my 85c's single action. Better yet, buy an 85c, send it Angus Hobdell for an action job and competition hammer, and you'll have a superb trigger in both single and double action. After I got my 85c back from Angus, I can say that its single action trigger is equivalent to a tuned SW revolver SA trigger.
Chris