Pond Boss Forums Thread Like Summary - Air pump question

I have an old 1/2 acre pond that I ran power to and installed a pump and two diffusers as a quick fix. I am now ready to install a better permanent system.
The diffusers are these: https://www.amazon.com/gp/product/B01G4BLYKS/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
They are installed with ~175' of 3/8" sinking hose in about 8' depth
The pump I used was this: https://www.aquacave.com/eco-plus-7-commercial-air-pump-280w-200l-min.html
The specs on this little pump say 7CFM and it has worked for the last year. How is it possible that this pump can put out 7CFM when a more substantial pump like this is rated at 4.5 CFM: https://www.123ponds.com/src50.html...zr9jmnhQtVr4_6ZdCSTHidkt8GoaAr4DEALw_wcB
What am I missing here?
the little pump is ~.375 HP, 280 watts, 200L/min and cost about $130 when I bought it.
The one I am looking at is 1/2 Hp and about $650.00
Thanks in advance for any answers

The EcoPlus is a diaphragm pump and will put out the advertised 7 CFM without anything hooked up to it. It's a "maximum output" that is deceiving since adding a line, a diffuser, and dropping it in 8 foot of water puts some resistance on the pump and that resistance will reduce the actual air flow through the diffuser. You need to locate a pump curve for the EcoPlus 7 to determine what the pump is putting out in in your scenario.

The rocking piston pump is very robust and can create much higher pressures, hence maintaining a much more consistent air flow in deeper waters. The SC50 only loses 1 CFM from the water's surface down to 15 plus feet of water depth. The EcoPlus will surely give up producing air by the 10 foot level.