Yes. It will be one or the other. Probably not the answer you want.
It’s too complicated to predict. Unfortunately trial and error is the final arbiter.
If "trial and error" is the answer I do not want, then I definitely do not want that answer! But if you are saying that a wall bass trap vs. a corner bass trap is too complicated to predict, I can deal with that. For me (and I suspect many people), room intrusiveness and effectiveness are the main consideration. I want the minimum impact into living space and aesthetics but with maximum acoustic impact. This is why I have left off any bass room treatment and only relied on DSP, but DSP can only get you so far.
What do you think the inputs that would be required to predict whether a wall trap is more effective than a corner bass trap, assuming both are pressure absorbers?
What I can say with confidence is don’t skimp on the quality of the trap based on the idea that positioning will give you better results. Size is only part of the formula for pressure traps.
Get traps that target the trouble frequencies, offer the best objective absorption and experiment with placement until you get the best results
What I have been thinking of for some time is to DIY my own bass traps, either a membrane absorber or a Helmholtz resonator. It would need to be tuneable. I am leaning towards a Helmholtz because it is easier to construct and easier to make it tuneable. All I need to do is to construct a box and place 5-10 BBQ air vents like
this (if a bigger hole is required, I can simply remove some air vents). But I am not sure whether it a Helmholtz resonator would be more compact than a panel absorber, or whether corner placement would make it more effective.
This is not strictly true; it depends on the thickness. The better products are 10-20" deep so they do provide absorption in the room. I have measurements showing midbass absorption with corner traps.
Velocity absorbers depend on thickness and the air gap from the wall, it needs to be 1/4 wavelength of the lowest frequency desired to be effective, and it rapidly loses efficiency under that. At least, that is my understanding.