Usually single stage compressors are rated at 90psi and 2 stage are rated at 175. The two stage compressors store more volume in a given tank size and can be regulated down to 90 psi. The pressure rating is not just marketing.
The receiver or tank is what stores the compressed air. There is no volume storage in either stage (or single stage). Two stage compressors are more efficient (compared to single stage) for providing higher pressure. If the two stage compressor has a heat exchanger (intercooler) between the stages, then it’s even more efficient than a two stage without intercooling.
Some manufacturers use the pressure rating for marketing. Why else would a company lead with 175psi when virtually no tools use that pressure? Why not just list the free air delivery at 90 or 100psi?
