Exactly - physics is physics.
It would be interesting to see a genuine comparison of see a TB20 against a 22.
On the one hand the u/c adds a fair amount of drag even closely cowled, but on the other, the airframe of a 22 is a good deal more efficient.
As to fuel I would be surprised if there is a great deal in it - perhaps a few extra gallons an hour, but I am not sure that is a factor for the private owner spending the best part of half a million dollars or more.
I am still not sure about the avionics concerns. In the Avidyne configuration in the 22 I fly there has only been one issue to date, the 42 had more with the G1000 but since these were sorted they have not resurfaced. Without doubt both Avidyne, Garmin, and Diamond seem to have resolved issues that occurred either with early units or aircraft.