Having driven Super Maramus with both MaxProps and AutoProps, I find little noticeable difference under most conditions from the helm. I know that theoretically the Autoprop is more efficient while motor sailing, but within the (admittedly very coarse) ruler of the dipstick measuring liters/day of fuel used I have not been able to measure a difference. I have also never seen the significant increase in boat speed at the same RPM that Burton claims in their advertising over a feathering prop, which has me question the whole assumption of greatly improved efficiency.
The one place where there is a difference while under power is in reverse. On a Super Maramu, the AutoProp has more prop walk than the MaxProp. Neither one has prop walk that is difficult to manage with the bow thruster, but the stern slides distinctly more to port with the AutoProp. It's not at all clear to me why there should be a difference, and it is not a difference which would make me chose one over the other, but it is there.
While sailing in light winds, at low boat speeds, the MaxProp is going to have a lower drag--but most Amel owners don't sail extensively in those conditions so that is likely an academic argument. Both will be dramatically better in this regard than a fixed prop.
The AutoProp has a reputation for being more sensitive to low levels of fouling, so might need more routine cleaning, but on the other hand you don't have to fully disassemble it to service the propshaft seal like you do the MaxProp. So net-net the amount of service work is likely similar, just of a different flavor.
In short, if they were priced the same, and there were no installation issues, I'd likely consider them a wash.
Charleston, SC, USA