There are also huge differences in the tax treatment of cubicles vs. walls, which can have a non-trivial impact on the decision making if it's an office of any size. Generally (and IANATL) cubicles and movable walls can be considered office furniture, whereas walls and doors are structural improvements - and those things have very different depreciation rates and benefits.
If you depreciate them, you have to either dispose of them at some point, or sell them at a loss (and you can only depreciate the loss). Over time it could cost more than walls, or have an extremely long depreciation schedule.
It's worth noting that modern offices often have the ability to place walls wherever their clients need them to be. That said, they are no better than cubicles because they have virtually no sound isolation.
Worked in the office acoustics world for awhile including coding a simulation for acoustics within both cubicle environments and private office to private office environments:
The most important sound paths in most office spaces are refraction ( low cubicle walls may as well not be there, just because you can't see your neighbor over a 48" cubicle wall doesn't mean that wall in contributing much of anything to sound isolation ) and reflection ( hard walls, cheap ceiling tiles, ceiling air vents with open air returns, etc ).
"Movable Walls" vary widely in their absorption profile, as do ceiling tiles. In both cases high quality models are fine. Most issues with movable walls had nothing to do with their absorption profile but rather poor installation/fitting causing 1/4" air gaps around the edges creating a perfect refraction and / or reflection path for sound.
