There are many kinds of scientific meetings, and much to love about (nearly) all of them.
There is the home society. For me this is the one I’ve gone to for over 20 years, and I have lots of friends I don’t see anywhere else. I get excellent feedback on my work. It’s a great society, that goes out of its way to be student and postdoc friendly. No one attacks anyone on the platform, but makes good suggestions (“did you think about doing X? It might really clarify some of your results”). 1-2000 people, almost everyone doing something Really Interesting.
There is SfN which is a world to itself. I remember when I started going, someone told me that while there were over 40,000 people, only half are looking for a job at anytime. SfN pioneered electronic planning, searching and programs. You can meet bigwigs, many of whom will even talk with you. You can meet littlewigs who have lots of good ideas (I hope they all get jobs). And all of the vendors have chocolate to give away.
There is the small specialty meeting. Make sure your ducks are in a row. Depending on the subdiscipline, it can be brutal. It can also be the most glorious intellectual experience of the year. Sometimes 20-30 people, sometimes 1-200 people. But if you are on your toes, you can talk to anyone, and come out with more ideas than you know what to do with.
There is the “let’s visit the other guy’s home society” meeting. If you are a physiologist go to the anatomy meetings. If you do genetics go to the taxon-specific meeting (ichs & herps, mammals, etc). If you always ASM go to the evolution meetings. This is good for keeping yourself mentally lubricated. Not quite so necessary or even advisable at the postdoc or beginning asst prof stage (in fact, it can be a real distraction).
Finally, there are the dreaded clinical research society meetings. Things like RSNA (Radiology Society of North America) which is worse than SfN with 100’s of 1000’s of people. Things that are more specialized (PD and Alzheimer’s). Things that are 400 people, and only 40 of them presenting. Sometimes I get something useful from these. But mostly it makes me glad I do research.