500NM range payload is a much better figure to compare performance…
Comparing airplanes is difficult to say the least. How exactly to do it most people have failed miserably in a general way. In principle, how you can compare airplanes is by mission or, as you suggest, over a fixed distance.
The 3 here are sufficiently similar in layout and mission that comparison is not that difficult however. All are travelling machines, all are IFR capable and the main question the OP had was how to get the most for your money.
Well, from a range point of view, the Commander 114 is the most limiting due to it’s fuel capacity. So to compare its quite good payload of 350 kg with 70 USG, one should compare the others @ the same fuel load and see how far they can fly with it, plus see how much further they can fly with full fuel at what payload.
I think the speed comparisons still are valid, as that is how most of them are flown. So still the SR22 is 20 kts faster than the TB and Commander with from what I see here about 2-3 gph greater fuel flow.
So now the important question would be, what is important to the original poster? How much he can carry? How far he can fly? e.t.c. and on the base of that, a new comparison can be done for the mission.
Full fuel payload is still a valuable figure to know, as it usually contradicts with marketing figures which will always give you top speed at WOT, Max Power and best level and range which will always be given at Long Range Power and much slower speed. If you want to achieve those figures, it is good to know that you can only do it with mostly a heavily reduced payload.
FWIW I don’t think the SR22 (NA version) is 20kt faster than the TB20 at the same fuel flow, but I would need to test it to get numbers. The only time I have flown with a higher fuel flow was for “best power” in climbing, or above ~FL160/180.
However, obviously, if you wound up the fuel flow on a TB20, it would no longer have the best-in-class range.
My view on choosing planes in this category is that they are all quite similar unless you have special requirements e.g.
If you are after seriously more mission capability, there is nothing in the piston arena (well, a Spitfire is quite quick, but being Annex 1 not useful for European touring ). The next step is really a Jetprop. But then you won’t be doing local jollies, taking pics, not least because you can’t get pics worth a damn through the windows of anything pressurised.
Comparing airplanes is difficult to say the least.
Passenger comfort and aircraft control harmony seem to be key subjective criteria which can only be established by trying out each type.
I sometimes decide which aircraft to use (of those available to me of course) by the cost per NM. That way takes into account both performance and fuel costs plus passenger carrying.
I must admit that I don’t always take the cheapest as my heart sometimes rulee.
These days I don’t have access to a 114b they are quite rare around here these days and the TB20’s for hire are becoming that way . Alrhough I have access to a SR22 it comes in at around the same price per NM as the DA42 so I choose that for longer distances. The DA40 tdi works out about half the price per NM but has nothing to do with this thread.