informal vs formal

Honestly, if you seriously want to be in a sorority and find the right place for you I would go through formal recruitment this year. Yes, being in a sorority is a time commitment but tons of pre med students do it. I'm a biology major (I'm guessing you are too) and 2nd semester and this upcoming semester was/is going to be so much harder than first semester. Informal or formal as a sophomore is going to limit your options.

School is never easier than first semester of freshman year if you're bright. Of course, if you had enough AP credits to enter as a sophomore, the way many of my sorority sisters did, then you won't have to take all of those typical freshman classes and it might be a different story. My high school didn't have AP classes (I went to a small, private immersion school) so I had to take the typical classes and they were easier than high school for me. But if you have any doubts about doing well, go through rush as a first semester sophomore. Skip informal/COBing because it's rigged and they aren't really looking for the best and the brightest, just friends of friends. You can do better.

I'm actually planning on majoring in physics. I have enough AP credits to enter as a sophomore and I''m pretty nervous! Do houses really discrimate against sophomores Active? Who would it be harder for me?

You sound like such a sweet, smart girl! I totally respect your reasoning for wanting rush 2nd semester, but if being a Greek is truly something you want to experience I'd advise otherwise. I totally understand being in pre-med it is very important to get a high GPA especially in the first couple semesters, but I can guarantee you that is a very feasible thing to do as a new member in a sorority. I 100% value grades and wanting to get a grip on things, but I feel as though learning to manage your time properly is a valuable skill you will need for all of college and being in a sorority will help teach you that from the start. The reason I'm being insistent on encouraging formal recruitment is because informal rush is very mysterious, non-transparent, and unlikely to receive a bid from. I know you said waiting until sophomore year to rush is something you're open to, but if you're like a lot of girls I know who did that you might regret it during your freshman year. Not everyone is lucky enough to make many friends in the dorms or in class and some girls just don't meet a lot of people. Some also end up feeling like their missing something if they aren't involved. I think you should definitely sign up for recruitment.

Rushing will give you a huge network of older girls in your sorority who can give you tips and advice on your classes, and most houses have study files which you can use to study old tests to better prepare. In your first semester, most houses require that new members complete study hours so while you'll be busy with hoco and such, you will also have a lot of resources that help you succeed in school.
Rushing as a freshman gives you the best opportunity to find the right fit. Rush is harder for sophomores because houses prefer to take freshmen, and only some houses will COB so you won't get to see all the houses that way. Plus COB is usually harder to get a bid without a definite "in" - in formal recruitment, everyone is rushing all the sororities whereas during COB everyone is wanting that specific house

Just go through formal to get a feel for everything, it's hard to informal rush especially since not every house participates in informal