That's a hard one. On one hand, going to Davis and having someone mentor your in an area of research may be worth paying a little more... but 70k? I guess it depends on what opportunities you'll have - will you get to run your own labs? Publications as an author? If this is what you'll get and you're looking to work in research after graduation, it may be worth it to get your name out there and get experience. Davis has an incredible reputation so having done research there and maybe even published with their researchers will open a lot of doors.
That being said, you can also do research at Purdue. They also have a great reputation. You might even be able to do your own research under the guidance of a mentor, even if their interests aren't aligned exactly to yours? This may allow you to do more than if you were working under someone with the same research interest (potentially). Are you able to reach out to some of the faculty there and see if it would be possible to do your own research? There's still plenty of time before the deadline to talk to people and see what's possible! And even if you go to Purdue and DON'T end up doing your own research, you can take that 70k you saved by not going to Davis and do a PhD somewhere, if that is something that interests you. Does Purdue have a dual degree option?????? Additionally, it sounds like you like their hands-on curriculum more... something else to consider as that is what you will be spending most of your time doing.
I'm having a similar struggle as I was also accepted to Penn (as well as Tufts, RVC, Michigan, and OVC and waitlist #1 at Ohio). I desperately want to go to Penn as it checks all the boxes for me: in a city, lots of opportunities for research and lab animal med, but also an excellent ECC department (another area of interest), close to family (in New England and Virginia), great reputation. However, I'm struggling with the fact that it's more expensive than some of my other options. I'm hoping there's a recruitment scholarship or grant out there for me because otherwise I'm going to feel some guilt accepting when I have options that are thousands of dollars per year cheaper. I know I'll get a great education and have opportunities everywhere I go, but there's something about Penn that makes me want to justify spending that much money. 🤷♀️
Sorry that was kind of long and rambling and probably not helpful, but I understand your struggle and wanted to give some thoughts!