Toured some big schools this summer. Not many will have a class size of 1000. Largest we heard was capped at 750, even though the room would hold more. (as if it matters, still farging big).
So here's the thing, as someone who went thru the big school. In a big school you can "disappear." Big classes, I would sit in the back and sleep, daydream and otherwise be distracted. Lucky for me it was mostly review as I had much of the material in high school. It worked for me. But I just got thru, kind of going with the flow. Didn't really excel. Didn't know any of my professors, etc. As I look back trying to guide my kid, it was just too big. These days they have all sorts of resources -- free tutoring, guidance counselors, etc. But you need to be motivated to seek them out. I don't think my kid will do that -- he doesn't even do it in high school.
We toured a small school. Had a one on one meeting with admissions for an hour. Really digging into the kid's interests, etc. Real personal attention. Mom fell in love with the place.
Can't tell you much about online. We where still programing in Fortran.