I'm a bit confused on setting manifold pressure and propeller RPM and the expected performance im supposed to get on both the Piper Arrow and Seminole. First with the Arrow, im looking at the power setting chart and it says if I cruise at 6000 ft and operate at 65% power I need 24" and 2200 or 22.1" and 2500 rpm. I understand the differences in manifold pressures but what I dont understand is which one to choose? Does 2200 or 2500 rpm provide any performance benefit? Why choose one vs the other? Same thing with the Seminole only now the chart ranges from 2100 to 2400 rpm. From what I can tell, I apparently I can get the same TAS say at 55% for either 2100 or 2400 rpm. So why the difference? Why choose one over the other?