College Essay for UMich, which ec should i talk about?

If you could only do one of the activities you have listed in the Activities section of your Common Application, which one would you keep doing? Why?

I want to major in astronomy and pursue a career in it. One ec related to it is in astronomy club. We talk about astronomy, give each other ppt presentations, and we plan on going on a stargazing session this year. I ran for VP few days ago, but I lost by one vote, so I am just a member. But I really like the club, we talk about lot of mind blowing stuff.
The EC that I feel is most valuable to me is a server job at a retirement home, I learned so much from just the environment, taking responsibility, communication with chefs, accepting mistakes etc. It is still a huge learning experience for me. I feel I have more in depth stuff to talk about, but since I am applying for astronomy major, I feel like I should write about the astronomy club.

So the question is, do I write about my major related EC or an unrelated activity that I would want to really keep doing?

Firstly, you should pick the EC you feel you will be able to write most authentically and enthusiastically about. An EC question is less about what you do, but WHY you do it- why is this something you’re passionate about?
However, if you feel you can do the above equally for both, I might suggest choosing your astronomy club, since it is related to your major and you can probably connect it to the school.