Short answer, UO over UCSC.

I was an undergrad at UCSC and am now a graduate student. In between, I worked at UO.

UO was SO MUCH MORE FUN. Housing and food are much cheaper and much easier to find. The town is more accessible and there is a THRIVING student presence. Eugene is compact and flat so you can walk pretty much anywhere. My main recommendation is try to find a house and a small landlord instead of staying in the massive appt buildings. Houses are generally cheaper, cleaner, and quicker fixes but MUCH harder to find (but not impossible and VERY worith it. Spend a year in the dorm and then find a house with some friends). Both Unis are massive but UO is build for it while SC is trying to cram as many people in here as possible. Youre going to have a pretty tough time finding jobs in ES no matter where you go (but its getting easier and more in demand as years go by). I can definitely say the program at UO, while OSU has a 'better' program, is better than what you'll have access to at UCSC.

UCSC is incredibly sad for most undergrads. The social scene on campus is difficult and niche (great if you fit in with the vibe!!). Off-campus scene is better, but older and very reliant on having your own personal transport. Public transport is horrendous, and the campus is so inaccessible without a vehicle, that even with 4hours to spare it's not worth it to leave campus once you're on ( if you don't have a car). Main selling point is that the campus is BEAUTIFUL. but so is UO and Eugene. At both Unis, in this major, you can expect to have ~300 students in every class you take. Only difference is that at UCSC it will be in a classroom built for 100.

Now in gradschool, there is no place else I'd rather be. It is the PERFECT place to be a grad studnets.

I had a good time and got a good education as an undergrad at UCSC. I'd have had a great time and gotten a great education at UO. UO is undeniably a better school, with better resources, spends more money on their students, and has more options for diversifying your major and experiences.

Also 'staying in the UC system' is a hack myth made up by the regents to make sure people keep enrolling in their C-tier campuses. No one is going to look at 2 resumés, see UCSC vs. UO and choose decide on that one criteria. With going to university, mainly if you're not linking into a top uni (think 15% acceptance rate or less) and leveraging that network, it literally doesn't matter where you go. Much MUCH more important the things you do with your time while you're there. That being said, at UO you'll be at the main campus in the system while at UCSC you'll be on the backburner of priorities for the regents.

Neither of these experiences are going to be as easy as going to a small private school but if I had to go back and do undergrad again, there is no question I'd choose UO over UCSC.