In ESB it seemed pretty massive (as did some of the shots we got of the regular Destroyer bridges), although I realize that part of that was a Matte painting-at least the big shot of Vader overlooking the fleet. Although there were extra parts that also gave it a larger sense of scale, such as the side consoles where the probe droid transmission is picked up, the place where Vader listens to the Star Destroyer captains etc.
In ROTJ it seems far more cramped, small, and the console seems to be actually in the way of the walkway. (I think some have said it would've made more sense for the guy to be in the crew pits as well, like the guy informing Needa of Vader's transmission in the SD Avenger). What's even weirder in the brief minute we get another angle ("We're in attack position now, sir") there's a wall behind him that makes things look even more small.
I guess it was cheaper to go with a more practical set, and the film was already matte-heavy as is?
I'm kind of reminded of the Star Trek films, although basically the same set the TWOK bridge looks more cramped than the TMP set, possibly for a more TOS feel they removed and rearranged some parts (Including Spock's station).
Now that I think of it we never really get any shots of the whole Falcon cockpit set either apart from close ups of Lando and Nien.