When looking at ERAS application packets (for residency interviews, and for fellowship interviews), I only pay attention to the EC portion to get a sense of the applicant's interest (and what they do in their spare time) ... it's also cannon fodder for interview discussion (and a way for me to distinguish one applicant from another)
/hey, you try interviewing 4-6 people a day, 30 minutes per applicants, for multiple days/weeks, and see how many details you will remember about the 30-50 applicants you interviewed. Grades, USMLE/COMLEX scores, LORs, all start looking the same. The EC will be unique and will help me remember people
//if you join too many clubs, then it's hard for me to really figure out which clubs you are interested/passionate about, and which you joined because it would look good on your application
///if you join no clubs and have no EC, then I'm curious what you did with your free time while in medical school (and can you handle work-life balance)
////overall, ECs make little to no difference in where you end up on the rank list. You can be the chapter president, but it won't change your standing. Holding national office is impressive, but wouldn't make up for any deficiencies in your application (and I have never seen anyone move up in ranking during our rank list meeting because he/she held national office).
///// yay 5 slashies. But seriously, join clubs/activities that interest you. Don't do it to impress or augment your application.
////// Research is a different beast and my above advice do not apply when it comes to research (esp if you are applying to university programs - not sure how much weight community programs will place on research)