First, both are great schools but boy are they different. I have fam working at CP, had 3 accepted there (but none attended) and best friends 2 kids attend. So pretty familiar with it and looove SLO, there often. I have several that went/are going to USC.
Bottom line, where do you want to graduate from? Where do you want to tell people you have a degree from? “I have a degree in engineering from xxx.” What do you want to say here? For awhile you will say it a lot, then not so much, but it’s still a lifetime achievement.
The idea that spring admits are second class is just silly and so not relevant. It’s basing your life on a perception of people that do not matter (like us on here frankly, ha). 70,000+ other students weren’t even offered spring. And I bet most of them would have loved to have had the option. Does their perception matter? They would say it’s fantastic. It’s your life, don’t live based on perceptions that may or may not be relevant to you. I get that’s why you are searching for info. But if one hasn’t had students in both schools or been closely involved in both schools in some manner, the data may not be so valid, or at least skewed. With lots of USC grads, of course mine is skewed to what I like about USC & private schools, we all have a bias. So you have to figure out what you are getting and what you are really giving up choosing one over the other. So my big picture view is -
Private v. public is incredibly different - ease of getting classes, ability to change major, double major, major minor - all eezy breezy at USC. USC engineering is very highly regarded and the project opportunities for students are insane because it is such a small department that is very plugged into LA industry and government. Mine had some crazy cool design projects, were members of some very special CS clubs, and one was also a TA who formed great relationships with profs. Great experience all around. Insane network waiting when they graduated (actually started career senior year).
No one knows or cares you are spring admit once you walk in the door, you are just another Trojan. I get you feel you will miss social opportunities, but I can’t believe you can’t replace those with others. Move into Gateway (they have less than year leases) and take a couple CC classes, go to the football games, etc., start connecting early if you want - staying at home isn’t your only option. Get on social media and connect with other spring admits. They have a special orientation to bond spring admits and try to house them together.
Lastly, I will say, if being a Trojan isn’t that important to you - that’s absolutely ok - but then maybe USC isn’t the right place for you. The students that go there, really really want to be there and know they want to graduate from USC whatever it takes. If that’s not you, then maybe CP is a better fit. So give that some thought, you fitting in (or not) may have more to do with not being that keen on USC than the whole spring admit thing. Something only you can figure out. Good luck!