Vandy or UCSD?

Hey everyone,
I was accepted to Vanderbilt and UCSD over the past few weeks and now I’m stuck with the difficult decision of choosing where to go. I plan on majoring in computer science and at Vanderbilt I got into the college of engineering (where their computer science program is located) but at UCSD I got into my alternate major, Math and Computer Science (Department of Mathematics). In order to do comp sci at ucsd I would have to transfer to the other department which is impacted as well so theres a pretty good chance that I might not be able to switch. Would that math and comp sci major be similar enough to the normal one? However, in terms of finances, I would be paying in state tuition for UCSD whereas I would be paying full tuition at Vandy. Would I be able to talk to anyone at Vandy about reducing costs?
I will be visiting both the schools later next week but I wanted to get outside opinions on which one seems like a better decision on paper.

In conclusion, UCSD is ranked higher in compsci and is cheaper than vandy but vandy gives me the guarantee of doing computer science and is a much more prestigious university overall; which one would you recommend I lean towards and why?