A scuba tank would be nice but options for compressors are limited. Y'alls input would be nice.
The CS4 is far more quiet then the YH. I haven't started my YH in over 2 years now. Plus with the CS4, and you like using bottles, you can take both with you, refill/top off your bottle while you shoot too... you'll always have air.I do not have a GX4 but I like my 3+ year old YH. Nearly all I use it for is filling my 45 minute fireman's tank. It takes less than 30 minutes. It is noisy but I measured the noise at less than 85 db so no hearing protection required. I think a tank refill with a GX4 will take several times as long.
I'd like to have both and would use the GX4 for gun fills and for traveling. May happen.
When you say "efficiently" hope you don't mean QUICKLY. "Economy" compressors need to be pampered & not pushed to go beyond what they're capable of. Authentic Yong Heng has been my choice & has served me well. No regrets. GSX4 owners seem to feel likewise. Either one will fill 4500psi SCBA carbon fiber tanks with NO problem.