If you are referring to the MHI Congress and Expo, here are some things to consider:
This is the largest attended event that MHI puts on so there will be more people there than at other events they offer over the course of a year. (This is an event of long standing originally started by Gub Mix many years ago.)
Many of the most valuable reasons to attend are held outside of the event itself and are usually by invitation only. (It would help if you could make friends prior to the event with someone who would be getting these invitations so they could get you in.)
From a community owner’s point of view, the day before (NCC Spring Forum) the main event is also very important. Unfortunately, you have to pay extra for it and cannot sign up for it separately.
There are going to be different opinions on this. I have been to all of them since their inception, and in fact have frequently been one of their speakers. Frank on the other hand, who has also attended some of them, seems to hold them in low regard.
There are other national events that MHI is not involved in that also have value.