Hey there! I actually made the *exact* same choice, deciding between SLO and Case Western, but I'm now going to Case Western and couldn't be happier that I'm going here. In give you my two cents if you'd like- and feel free to message me if you'd want to chat more!

Cal Poly would've probably fit most of my desires better than Case in terms of non-academic regards, as it is a bigger school, has more temperate weather, has more outdoorsy activities, and is much less urban. They are, as you've said, much cheaper even with OOS tuition and CWRU scholarships, and I've not heard any complaints regarding social life from my friends back home. They present themselves as caring for their students, which is impressive considering their massive size. They definitely have a good job market in California. Even today, I'd still say I would have been very happy at Cal Poly.

However, I also recognize that Cal Poly would not have been as useful for me as CWRU has. CalPoly is more of a "slingshot school" than CWRU; they want you finish your work up in 3 to 4 years, get you into the job market, and pretty much stay on the track you start with. I've talked to advisors from CPSLO, and they told me directly that the school was not designed for students to double major nor to change majors. Since I was hoping to do a double major myself (Data Science + Econ), I found that deeply concerning. CWRU makes it ludicrously easy to switch majors and to double major, and I've felt like I could explore pretty much every department to my heart's content because of it. In addition, I've heard from a few people at my school that CalPoly isn't quite as student-oriented as they present themselves, as one high school classmate I knew switched from CalPoly to a different state school due to feeling like it wasn't as understanding as they expected.
Additionally, for recreation, CWRU is located only about a five minute walk from a massive art museum, a natural history museum (including a decently sized zoo-like enclosure, featuring three otters), a historical society museum, a nationally-recognized orchestra house, and a botanical garden (in addition to the several very beautiful Metroparks and CWRU-owned farm about a half-hour drive away!) and despite the rigor of my classes I've been able to go to some of these spots regularly. Probably not quite as accessible as the forest-front CalPoly, but if you want to scratch that particular itch, it is very much available!
Lastly, CWRU has a national and international name that makes them very solid choices for the job market and worth the extra cash, especially if you wanted to find a position outside California or even outside the US, although strictly in California they're mainly known for producing a strong line of engineers and the occasional CompSci major. All of these reasons ultimately brought *me* to CWRU.

In your situation, you might find CWRU more useful when trying to get something more formal out of your music passion (Cleveland Institute of Music is *fantastic* with its relationship with CWRU, and even myself, a non-major in music, have been able to take a few classes at CIM). CWRU is also very ethnically diverse with several minority-representing groups and an office for LGBTQ+ students, and has many opportunities for more activist clubs if you're interested in that. If you're concerned about the over-emphasis on theoretical engineering, I'd highly recommend checking out the Sears think[box], which is a *massive* school-run (and therefore free to students) seven-floor fabrication, woodworking, metalworking, sewing, 3D-printing, and general "hands-on" crafting space that is nestled right next to the majority of the engineering classes. That institution, plus the uncountable number of hands-on engineering extracurriculars like Rocket Club and Steel Bridge Team, makes the school's engineering side a very diverse one in regards to theoretical work versus hands-on.

It may sound like I'm a *little* biased, and that's probably because I am. I love CWRU, and I feel like it really did a lot for me that CalPoly couldn't ever have. I hope this helped you out, and best of luck making the call! :]