Pros
I really liked the internship experience at CBIZ MHM in their SF office, they really gave me a hands-on experience with audit work that I think the Big 4 don't really give. I was treated like an associate in terms of the work I was given. For the summer, the office works mainly on EBP audits, so I didn't get much experience working on actual financial statements, but I think most public accounting firms don't work on financial statements that early in the year either (summer). Pay was quite nice. Location was nice as well; office is right next to the BART station (in fact the station connects to the basement of the building). My seniors were quite nice and treated me like an adult.
Cons
Big 4 has more competitive pay, at my internship with PwC this summer I will be paid $41 an hour compared to CBIZ's $35 an hour.