I respectfully don't think you understand how regulators are serviced or how they differ.
Perceived work of breathing in a properly functioning regulator is chiefly determined by how the second stage is adjusted. It is possible to discern a difference even with a very small change in adjustment. A regulator that is tuned to open at 0.5" will breathe very easily and well but will be prone to dribbling air, will freeflow easily if not in the diver's mouth, and will be prone to freeflowing if the diver is in an inverted (head down) orientation that places the exhaust above the diaphragm. A regulator tuned to open at, say, 3", will have none of these problems but will breathe extremely poorly. I tune my primary regs to 1-1.5" and my secondary regs to 1.5-2". Tuning tends to drift with both time and use. The passage of time causes the seat to reshape slightly due to cold flow. Use causes it to wear. Either will lead to the reg running hotter (opening closer to 0) and therefore breathing easier. If the reg is tuned fairly hot (closer to 0") to begin with, then time and use will lead it to dribbling air and otherwise behaving badly.
For externally adjustable regs, this can to some extent be compensated for by turning the knob. On my HOG classic, the only externally adjustable reg I have, the knob makes a difference between cracking at around 1" and cracking at around 2.5".
Adjustable or not, the tech who sets up the regs after service (or when new) has to choose a compromise. Set the reg too hot and over time the reg will dribble air and freeflow and the customer will become unhappy. Set the reg too cold and it will breathe badly, and the customer will either not notice or blame the reg. So most techs start out setting regs fairly cold. And that has much more to do with how regs breathe than what brand it says on the sticker.
