Advantages to multiple meeting halls:
1) Your dwarves will be more spread out in case of emergency/lever pulling/ new work to do.
2) Your dwarves won't make friends with each other as fast, and may form friend groups that don't interact much depending on how your workshops/bedrooms are laid out. This is a good thing
3) Traffic. A meeting hall with a one tile exit can be a bottleneck for traffic if everyone has to get in and out at the same time.
4) Quarantine. Deadly blood is contained to one meeting hall at a time, and worst case scenario you can brick everyone in and then take the time to flush it with magma.
1) Setting up all these meeting halls and making them all expensive and lush is pretty time-consuming.
Personally I have well meeting hall and an enormous dining room and several smaller dining rooms spread around the fort so that dwarves with extremely limited remits can live in small burrows.