I think you’ll be fine with the cheaper one.
When air escapes from a nozzle the psi is essentially zero. So psi creates air flow.
Some machines have a nose cone where the air is forced directly down into to cut. Others use a tube that kind of does the same. Getting air into the burn zone is key
I’ve tried moderate and higher air flows and didn’t see much of a difference in the cut. There is a huge difference between no air and moderate air. Soft woods will burn around the cut with no air. Btw my experience is on a 50 watt CO2 unit.
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