It's pretty simple. Going to the cheaper school will in no foreseeable way screw you. Going to the more expensive school might screw you. No foreseeable way > might. Go to the cheaper school.
Happiness in medical school is something they try and sell you in the brochure. You're going to be studying your ass off for 2 years, disappear into the hospital for 1.5 years, interview like Hell, and then spend 3-4 months blasted drunk. Congratulations, Dr. devolution. Were you happy?
I've been reading this debate for awhile...It's very interesting how polarized the opinions can be on either side.
My experience is that many factors should be considered and that money is not an ultimate trump card. I personally see 10-15k a year difference as pretty negligible if there is a large difference in how much you want to go to a school. This "dream school" mentality is really up to the individual, which is why this debate can get frustrating-everyone prioritizes different things.
As generic as it sounds, every single one of my academic physician mentors (5 from 3 different academic medical institutions, all in the "top 20 med schools" by USNWR so keep that in mind for their bias...) has told me that if you get a shot at a top-10 med school, you should take it no matter the cost because of the doors it will open.
In their opinion, extra-ordinary careers are built on extraordinary schools. Not saying that every person from these places will go on to be great, or that people who don't go to these schools can't be great. But the law of averages over time supports this statement.
Before you jump down my throat, I don't necessarily agree with this in every instance and money was a huge factor for me (I couldn't have attended my school without a great package). But I think it comes down to your career goals and I do think that reputation of the school should be considered. Residency placement isn't all Step 1, I know some people think that, but IMO and the opinion of the different departments I've worked in, it isn't. I've seen all the counter-arguments: selection bias on match lists, inbreeding, geographical preferences for state school students wanting to stick close, etc.
Work hard, pick a place where you feel supported and where you can be happy. Different institutions draw different types of people and have different themes. I do think the curriculum is an important factor- the idea that every medical school "uses the same powerpoints" and therefore every place teaches EXACTLY the same way is (IMO) not at all correct. The idea that the faculty makes no difference is not correct.
Pick a place where the students are cohesive and happy. It's four years of your life and medical school is not just a "guided independent study" experience. It is a time where you are going to develop all the knowledge and instincts that will carry you into residency and being a physician. It is a time where you will make career-lasting connections. It is a time when your experiences and clinical exposure will help form personal opinions on what specialty you will go into that will dictate your entire future. It is important.
Good luck with your decision!