The advantage of the larger school in my experience, is that its like going to a dozen small schools at once. Plenty of people I know where able to transfer from one good program to another in a completely opposite field once they learned what they actually liked (usually quite different than what you imagined as a highscooler especially if your parents have no concept of the field), because the school was large enough to offer so many good options and departments with a lot of interesting faculty. The class sizes are the same between big and small schools anyhow for the most part, but you also have an easier time scheduling classes (and taking certain ones “out of season” if need be) at the larger school. It scales horizontally rather than vertically as your student body increases, big schools have the pockets to hire more faculty and support more taships than smaller schools.
I think you and GP are using different definitions of "larger". One definition is "more programs". Another is merely "more students".
Generally, go for the one with the lower student:teacher ratio. My anecdote:
I and a friend both went to low ranked undergrad universities (state schools). Mine, however, had a low student:teacher ratio per class. Comparing notes with him, the main benefit was that professors actually cared about teaching. The number of students wasn't high enough to be a burden. They didn't repeat the same HW and exams every semester. The number of office hours per week per professor was 3-9 hours. They could be that generous because there simply weren't enough students to use up those hours.
We also didn't have TAs teaching any course.
(Also went to a top ranked university for grad school - very few professors cared about teaching).
Yep, I attended a lower-ranked state school for an undergrad in CS and had a wonderful experience. Lots of positive interactions with faculty in CS and math. My undergrad school was also attended by a large population of highly motivated students for historical reasons. I stumbled into this school almost by accident and was really happy with my student peer group because most were quite ambitious.
I also then went to a well-known and ranked R1 university for grad school. I didn't enjoy it very much but also didn't match well with an advisor out of the gate. That colored my experience significantly and in hindsight was really mostly my fault.
Oddly enough, I returned to this school and work a somewhat hybrid staff/research software engineer job and have been here for more than a decade. Go figure.
Agreed re: "large enough to offer so many good options and departments." This is definitely a big pro in our opinion. It is definitely true that smaller schools are more limited in offerings than big schools. During visits, smaller schools seem to carefully point out some flexibility in putting together a more personal course-of-study to offset this . . .
