You really can't gauge fuel consumption differences very well between engines in the same series in the field. There are too many variables. Grass height and moisture, humidity and temperature. The settings on the carb and the wear of the parts. Your findings really only apply to your 2 mowers and are not representative of commercials vs standards in general.

You will always be burning more fuel when running at a higher RPM with your mower. That is unless you are bogging it in tall or wet grass and the governor is opening up all the time.

Do they use the same engine or are the engines the same displacement and compression ratio? Does either mower power the wheels? Lacking information like that it is anyones guess. You were fooling around and doing some testing so you apparently have both mowers. Why don't you set up some serious tests using measured fuel under free and load conditions and report the results.

Thanks for the follow up gents.I was gonna run both under load with fuel amount in deluxe transford over to the commercial but i didnt wanna do it till fall when i need to get rid of left over fuel.Inother words i didnt wanna waste it now until im done for season.Would be interesting though.
I can always just run the tanks empty and see how long each mower runs from gas from the carb i guess.

I believe the commercials using the Duraforce were exempted from the EPA regs and ran richer. The ones I have seen running were running like the old LBs and blowing smoke - very 'healthy-sounding'. Every residential Duraforce I have seen ran slower and rougher UNLESS it had been modified with larger orifices. So I'd have to reason that the average commercial Duraforce runs richer than the average residential Duraforce.