This is a pretty broad question, and much of it has to do with your personal preferences regarding work environment. A large program means a large institution, which means you may not get to interact with and know many of your colleagues, chief residents, program directors and attendings. Large programs sometimes also means several clinical sites, which further exacerbates this problem and adds in the problem of learning multiple hospital layouts, nursing staff, computer systems, protocols, etc. I am struggling with the big program vs. small program because I'd like to really get to know all my colleagues and feel like I "belong" on staff at one or two hospitals. However, I really need a major academic program to meet my goals, and those are usually larger in size.