There is so many variables that there is not a single easy answer. As for the 1650 (esp. in
the B model) it depends if it the -3 or the -7 series. The -3 was the "high" altitude engine
and the -7 was the "medium" altitude engine. They would have different flight envelopes.
Are the performance numbers your looking at using 100, 100-130 or 100-150 PN fuel?
Those are some things you need to specify before a comparision can start.
Of course what can be said now is the engines are two different breeds. The 1650 uses
a 2 stage 2 speed supercharger that is gear driven. The 605AS/D uses the enlarged
single stage supercharger from the 603 combined with a fluid coupling. Both have their
advantages and disavantages.
The 1650 uses a lower compression ratio with higher boost pressures whereas the 605
uses higher compression ratios with lower boost ratios. As I understand the theory is
both had relatively the same combustion chamber pressures, but I'm not an engine man.
The 605 has direct fuel injection into the cylinders...still the best way to get efficiency, plus
with injection the fuel is atomized by pressure; thus lower volatile fuels can be used.
The 1650 use what is call an injection carburator and the fuel is helped with atomization by
going through the supercharger.
The 1650 is a 27.02 liter engine and the 605 is 35.7 liters.
That is the beginnings to an answer.
From what I have read and studied in overall performance
I'd be more inclined to say the 109 had the upper hand at lower alt. (20-23k) and the Pony
had the upper hand over 25k. Really I feel they were pretty evenly matched aircraft and
the one that had the advantage usually won the battle.
IMHO and FWIW