So I don't MU anymore. I RP on a GTA RP server these days. It's different in a lot of ways and the same in others.
But this is where it really really differs. I have been at and run events where there's so many people that area of the city is crippled and framerates struggle. We're talking 50-80 people in one spot. But since you can only hear in a limited realistic range you end up with more realistic clusters of people interacting.
I don't miss the days of 'I have to respond to everyone here or else someone might get upset at me' and I love the realism of going 'hey guys I see a friend I'll be right back' and running off to greet that person. You miss out on stuff yes absolutely but it's not in your face that you missed out.
Also scenes don't last twelve hours and it's a million times easier to just bug out.
Big events are one of the things that keeps me in this (still new to me) environment. I had stopped attending them altogether on MUs due to a lack of mental capacity. Now I'm running them again on a regular basis. It's refreshing.