If you are relatively low on memory (512 megs or less would be my guess), it does hurt, because ET still asks the OS for 256 or whatever, causing other stuff to get swapped out. ISTR there is some hardlimit for hunkmegs, i.e. if you set 512, ET still only asks for 192 or 256 or something.
I don’t think I’ve ever encountered a map that wanted more than 96.
It does seem that ET may do its own swapping/caching sort of thing as well, so if you only have hunkmegs 56, it will grab things off disk more often, and you only get the hunkalloc error if there isn’t enough room for everything it needs simultaniously. (thats speculation. I’m pretty sure soundmegs memory behaves that way.)
Note that hunk doesn’t account for all the memory used be ET, either.