No. At least, not as far as anyone has been able to determine. And the Rev. 3 (usually called Rev. C) ROM has an issue with some kind of network expansion card (not a common card) which the Rev. B did not. So Rev. B is probably the sweet spot.
BTW, the way to identify the ROMs is to read the numbers on the ROM chips on the ROM DIMM. OWC put up this big ol' web page on identifying the ROMs and how hard it is and they went on and on about the circuit board part numbers and how they could be one revision or the other. If they had bothered to look at the part numbers on the CHIPS all the ambiguity would have been gone.
Unfortunately, it's been so long since I worked wtih them, I don't remember the part numbers. The Rev. A is something like 343S0401 and 343C0402 or maybe 341Sxxxx. I think the Rev. C was 343S0494 and 343S0495 but again, that's from memory. I never knew the Rev. B number.
Ah, I found an old post of mine on the topic from back when I remembered this stuff. The Rev. C does not work with Skyline Brand ethernet or wireless products. I can't find an old post that lays out the chip numbers though.
The main difference in the Rev. A motherboard from later motherboards was the video chip. I think it was Rage II vs. Rage Pro and later Apple went to the Rage Pro Turbo, but never took advantage of the Turbo's extra features in software so there's no difference in practice between the latter two.