I think the difference was supposed to be that Holograms are basically NPCs with software that can convincingly pass a Turing test, but there really isn’t any light behind the eyes. Androids are actually sentient, and their personality and emotional states are extensions of that sentience.

One of the implied questions of Voyager, at least to my mind, is if that distinction makes a difference? Especially in S1, it was clear that The Doctor wasn’t respected by the crew because everyone knew intellectually that he was just a chatbot.

I bet the inclusion of “bio-neural circuitry” in Voyager was initially intended to give some meat to the claim that he’s more than just software, but they never went anywhere with that. By the end of the series, it was pretty much settled that The Doctor had personhood. Star Trek’s implicit stance on the matter of ‘should you give a being rights’ is if it quacks like a duck, treat it like a duck.

Edit: Formatting