Northwestern is the richest school with the biggest endowment of all the schools you listed, so this shouldn’t be terribly surprising (and it’s an Ivy-equivalent by any metric anyway).
The Ivies have done a terrific marketing job, but sometimes, you have to recognize that a marketing job is a marketing job.
In any case, you should take out the loans when comparing fin aid offers (because you have to pay them anyway and you can get the same amount of direct Federal loans at any school).
OP that is a great list of schools, and your COA is in perspective, very low. I do understand you have very tight family finances with what is earned and household size.
Looking at Kiplinger’s Feb 2015 ranking and costs, the total cost (full sticker price) to attend these schools is all in a pretty tight cluster, $61,834 to $63,554 per year, so to have your cost at Northwestern be $5400 for the year is outstanding.
Kiplinger’s top 50 private universities had all 4 of these schools rated very high - Cornell at #12, Brown at #13, Northwestern at #20, and URochester at #28. Cornell’s UG student body size is 14,393, then NW at 8,688, Brown at 6455, and URochester at 6,177.
If I were your parent, and nothing changes on the four FA ‘appeal’, I would say go to Northwestern or Brown with no loans. I like Northwestern better, but you have to decide what appeals better to you. If you saw advantages to URochester, the extra out of pocket (extra in contribution if it could be done, or the gap loan) in comparison to Northwestern and Brown.
I think you honestly have to look at these three most affordable schools as your options unless Cornell changes their FA on your ‘appeal’. You are fortunate that the amount of your loans/out of pocket to attend any of these four schools is relatively very, very low.
A few years ago, my friend’s DD really liked Cornell (would probably be full pay, ouch), but was the last class to have the ‘free’ no tuition at Cooper Union (which is much harder to get into). They took another look at both, and parents were greatly relieved DD chose Cooper Union - she is EE and is loving it. Has a great summer internship lined up. She is completing her second year. As you, she had a lot of great college choices. She made the right choice on many levels.
Let us know where you decide to go, and if you received any change in FA. Best wishes to you.
BTW, your opportunities as a ChemE at Cornell will be about the same as your opportunities as a ChemE at NU, so if you do pay more, know that you’re doing so for fit, etc.
@cptofthehouse - Yeah, I made generalizations, but I have learned my lesson now. Thank you for the info! 
@thumper1- My original issue was Cornell was my top choice, but it was the most expensive option. In the larger picture, yes, Cornell gave me a great offer and I am grateful!
@PurpleTitan- I definitely believe my choices are equal in academic strength. As you said, “fit” will probably be the deciding factor.
@SOSConcern- Cornell’s website says they match all ivy leagues, so they would match Brown’s offer. So as of now, I think my schools will be in the same ballpark for costs.
Thank you everyone for all the info, it really helps! I just visited Northwestern over the weekend, and I really liked the campus atmosphere. I will wait until visiting my other schools to make my final decision, but I will keep you all updated
Great news OP about Cornell matching Brown’s offer. Hopefully you will complete UG with very low cost and low financial strain on your family.
Glad you will visit the schools before your final decision.
Another point to make is the school that really wanted you on campus may be another indicator of a ‘match’. My kids got great scholarship offers where they really wanted to attend, so a win-win. See what feels ‘comfortable’ to you and where you can reach your goals through UG and beyond.
I do hear about the large classes in the beginning years at Cornell, and not always taught by professors - or a lot of student contact with TAs.
Try to talk to other students too on campus.
Envision where you will be happy, and also see what your parents think.
@SOSConcern and others
Update:
I chose Northwestern! FA ended up being the same for all 3 after appealing twice at each school. (COA being around 5k)
Northwestern had the best programs for my interests— ChemE, Material Sciences, Nanotech. I’m also interested in IndustrialE, Economics. I love the sound of Kellogg Certificate with an engineering degree. Double majoring seems to be much more doable b/c of Quarter system.
Also outside of academics, I liked the suburban but close to Chicago location, diversity of students’ interests, and campus size.
Not many people around me know what Northwestern is, so it was kind of tough choosing it over 2 ivies (pressed the commit button on April 30). But name recognition (hopefully) won’t really matter in the long run.
Thank you all for your advice!
Congrats and excited for you @sugoi15 - sounds like you have some great opportunities at Northwestern.
Don’t know if Milwaukee School of Engineering (MSOE) is still on a quarter system - that was pretty traditional for engineering programs in the past…eventually schools like Ga Tech and Auburn switched to semester format (maybe early 1990’s). H graduated from MSOE under quarter system (he worked summers), and his practical abilities/specific knowledge/experience with a specific area of study had him with a job in hand early in his senior year from on-campus recruiting (large OOS company) even with an ‘eeking by’ GPA - H is independent learner vs classroom.
You have the academic chops, so just keep looking at being ‘marketable’ - having the practical applications of your field(s) of study that industry is looking for.
Chicago and metro area is the jewel/thriving industry and economic thriving of IL. After you get some schooling under your belt, you may find summer internship opportunities too - not sure what is available in your parents’ area, but maybe you will have opportunities utilizing NU partnering opportunities.
@SOSConcern Thank you so much! I am so excited to start school next fall.
The fast pace of the quarter system is definitely intimidating, but I think overall the pros outweigh the cons. (I want to try to squeeze in some economics classes if I can). I will definitely try to brush up on my calculus, physics, chem and bio this summer.
I agree, I am a very practical person and like that Northwestern has a pre-professional focus. The cool thing about Northwestern is their Freshman curriculum includes a hands-on design project and building up practical skills along with lectures.
I live in Ohio now, and there are some big companies here. I prefer to stay in the midwest so NU seemed like the best option for me
Northwestern is a great choice. Our FA package was very similar for a family of 7 with the same approximate income.