MyDay
Hey MyDay,
I actually wrote a response similar to this in the QCE area here. I think extracurriculars are not only really good for university admissions but I think its really good for developing skills, your mental health and a good use of your free time.
If your degree is competitive and/or has an interview, extra-curriculars are a big boost to your application, and even more for scholarship applications. Its boosts your chances at internships, placements, bursaries, scholarships etc. It shows that you have commitment, organisation and a wide range of skills.
If I were to recommend a type of extra-curricular activity good for university admissions, it would definitely be something service related. Something like fundraising, helping disadvantaged communities, assisting with advocacy etc. No one told me this but I joined a service activity because I thought it would be fun and where I could create a large impact. And frankly, you would be wasting your time if you aren't enjoying what you do so don't join extra-curriculars because it looks good; only do them if you enjoy them. I also think music/sport shows good commitment and skill because it shows you're not only doing academics. If I were to recommend one that is directly beneficial for you and your academics, it would be chess. There's so much scientific support on the benefits of playing chess including cognitive development, concentration increase, critical thinking etc. I could go on forever about this...
As @Sine said above, you can certainly get into most competitive courses if you just have the cut-off marks but its always good to have a strong extra-curricular background because it will always give you something in the end. Having said that, you need to ensure you are organised and maintain your first priority as your academics if you are looking to get into a competitive degree.
Anyways, hope this helps!