In my completely biased opinion as a Vassar student, I also think the Liberal Arts colleges offer a connection to profs and research at undergrad level that a school like Cornell doesn’t. Even if you were offered a place at both, your post makes it seem like you’d only go to Cornell for the name? Would that really be enough to keep you happy for four years?
Your “connection” to Cornell through your sister is so tenuous that it will have zero impact on your application. Please trust me and the many others who are telling you this.
More importantly, why are you even asking this question? Vassar sounds perfect for you and is a great school.
I LOVED Vassar when we toured it with my son. He also wants to major in science, so we met with a science prof. I was blown away. I expressed concern about whether a small LAC would provide the same research opportunities as a university. He grinned and sad, “That’s my job!” He then told me about the different students he had helped network to find summer research positions at top universities and hospitals. He said that is not unusual at Vassar; students develop strong relationships with faculty. I can’t tell you how different my experience was at an Ivy League college.
If you think you would thrive more at a small liberal arts college, trust your gut.
I agree with everyone saying that having a connection with a school isn’t in itself a compelling reason to prioritize it. I also agree that the connection as described is unlikely to move the needle. Perhaps most importantly, I agree that you have offered far more reasons for preferring Vassar anyway. I suspect your dilemma has something to do with Cornell being the more famous school, but Vassar is a great and highly regarded school too, and really what you do in college is many times more important than the name. Also I believe you will eventually find that although universities and Ivies in particular are better known in the general public, top LACs are often just as well known amongst those who may have more direct impact on your career if interested in something that requires graduate education (eg, medicine, law, or academia), because these LACs tend to send disproportionate numbers into those careers. So my advice would be to prioritize based on where you think you will be inspired to make the most of the college years. That said, if there really are good reasons to apply to Cornell (ie, it actually offers something important to you that Vassar doesn’t), it looks like Vassar has two rounds of ED. For schools with two rounds, I believe there’s a slightly bigger bump for the first, but that’s based on anecdotes rather than hard data I have seen.