Increasing pressure in an already max loaded cartridge is not gaining anything.
Jut as a point of procedure, the above is factually incorrect. Of course something is gained, velocity. While that gain is a matter of a diminishing returns vis a vis load pressure, let us remember that in all of our energy calculations the most volatile figure is velocity, which is always squared.
I agree with your assertion that simply moving up in caliber is the best way to achieve more energy on target, however I can't put a .45 in my jeans pocket, the same cannot be said of a 642.
So, IMO, if in any instance it is a given that the caliber may be fixed by other influences (A .38 fits in a pocket, grandad left you a .38 and you can't afford a new gun, etc, etc),
in the caliber you have, more velocity = more energy on target = a greater chance that you go home.
Or more simply, all other things being equal, mo' faster is mo' better