All things being equal between two applicants ... Most colleges will pick the one with the most extra-curricular activities.
HOWEVER ... They will also look to see if those extra-curricular activities could benefit the college. So if the college needs a football player rather than a band member, the applicant who played football will more likely be chosen.
That all depends on the particular college and the rest of the student's experience/grades/potential, etc.
Colleges like to see students who are well rounded. So yes it could be an advantage. Especially if the applicant was going for a music degree, or had no other extracurricular activities.
As someone who was in your situation back in high school except with orchestra instead of band, I would say that it does help especially if you can somehow show that this experience was beneficial in improving your work ethic, in shaping the type of person you are today, or for any other qualities that the college may be looking for. For example, when I wrote some of my admissions essays, I wrote how being in an orchestra made me value teamwork, being section leader helped with leadership skills, and participation in competitive orchestras that require audition widened my scope and knowledge about culture and stuff like that. For the Common App essay where they asked what's the place you feel the most comfortable in, I said the bathroom because that's where I practice my instrument (because let's be honest, they have great acoustics) and I mentioned my orchestra accomplishments through that (also most people wouldn't say that the bathroom is their favorite place so it made it unique).
Most universities these days look for well-roundedness so if you have good grades, being accomplished in band will just work in your favor. However, if you don't have good grades to go along with it, then it won't do you any good unless you're planning on studying music. Honestly, there isn't one formula to get into a good university so the best thing to do is to try to play all the cards you have and be the best candidate you can be such as by getting good grades, having extracurriculars, doing volunteer work, obtaining leadership positions, participating in competitions or research (especially if it relates to your potential major), and performing well on standardized tests.
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