Software in ROM is worse, since you can't pull vendor updates to fix any security bugs and you can't reverse engineer it, produce free firmware and replace the proprietary firmware.
And then we fall on the whole subject we're discussing here. In this particular case, a "power controller chip" I can even consider a fix or a change that improves efficiency... Nevertheless, I doubt most devices allow the update of a firmware for such a thing, in the end, it wouldn't make much of a difference.
If the firmware is open source, sign me in! No opposition! Neither from me nor from the FSF. FSF would not oppose libre firmware.
If it is not open source... well, then this is discussed in the other comments.