Well, when you record in a professional studio and get to play with a professional rack chorus, which gave these lush wide dimensional stereo effects, it kinda sucks to go back to a Boss analog chorus. We now think those sound lurvy in their own right, but we also now think digital is a curse word. As with delays, if you wanted a delay that you could dial in to the millisecond, with modulation, a Boss DD-2 or an analog delay isn't going to cut it either. As I said, in those days guitarists didn't want vintage tone, they already had that. They wanted more gain, more controllable delay time, wide spacious chorus. Only racks could give them that. The quest for tone was always around, only the goals were different. Personally I find their quest more interesting and better then today's quest.
As for the Muff, if Kitrae says Edge uses a V5/V6 I must bow to his authority. I never could see that tone bypass switch so I thought it was a V3, maybe a V4. The tone bypass switch could explain that huge BtBS sound. As when you bypass the Muff's tonestack you don't get its associated volume drop. Nor the midscoop. So it will sound huge. And somewhat less then a Muff. The op-amp version sounds somewhat different, at the time most people didn't like it, but as I said the Smashing Pumpkins changed that perception. Which leads me to theorize that there are no good guitar tones, only famous tones. And that if you or I ever became famous guitarists, our tones would become desirable too, no matter how we obtained it. Even you with your tiny Digitech thingy.
The Muff being a distortion or a fuzz, that's a very old debate. Circuit wise its a fuzz, but not one of those simple two or three transistor fuzzes that comprise only a handful of parts, it's got a lot more components, and also very unique among fuzzes a tone knob. Unlike most fuzzes the sound is not determined much, if at all, by the choice in transistors. With a Fuzz Face it stands or falls with picking the right transistors. In a Muff almost any transistor will do, as long as you keep the pinout in mind. It's the other components that can make the sound. It also differs from most fuzzes in that it doesn't mind if you place it behind a buffer. So it kinda works like a fuzz, kinda sounds like one too, but it also kinda sounds like a distortion. And like a distortion it has a shitload of gain.