On the limits of sizing loudspeaker drivers to enclosures. How big is too big?

It's a simple question. Assume you had a cuboid enclosure 5in on all sides (for example), assuming no real mounting requirements, meaning a driver with a diaphragm diameter of 5in can be used. Is there any reason grounded in acoustic physics to choose otherwise? We all know of the low frequency and SPL benefits of a larger radiating surface. Assuming these benefits are what you want, and the ideal nature of this question means you can have the driver dia = box face dimensions, will you do it? will you use the absolute largest possible driver that can fit, or will you be more conservative in choosing the diameter - opting for a 4.5in or 3in woofer instead?
Remember there are no mounting or mechanical concerns. Only the (potential) drawback of having the sound quality & properties change - or be colored - due to the lack of a real baffle around the diaphragm (since the driver is effectively edge to edge on the mounting surface). Is there any reason to say "No. Even if I CAN have a 5in driver on a 5in enclosure, I WON'T, because..." Logically, bigger drivers mean better sound, if there were some magic passive radiator that could tune the woofer to any given frequency, should you have a fun field day and go for the biggest that would fit, or is there some other benefit to using a smaller driver (lets say with greater Xmax - giving the same displacement).

TLDR: If you can have A, will you still choose B? And Why?

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TLDR: If you can have A, will you still choose B? And Why?

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In such a small enclosure, A will sound constricted, boxy and not go down enough.

B will sound flatter and reach deeper, although it won't be too loud.

Don't worry much around so called "front baffle", in both cases it is still 5 by 5 inches, and this is not an infinite baffle by any means, but a sealed cabinet, main parameter here interacting with speaker is internal volume.

Which in both cases is about same.
 
OK, I thought the thread starter was discussing if big drivers should be preferred to small ones if enclosure questions play no role concerning dimensions.

Due to qts the big Fane could take large Volumes.

Sorry for not understanding.