Dear OP,
This is one of those decisions you only get to make once in a lifetime. If you choose wrong, you could wind up sleeping in a gutter in Tiajuana having just prostituted yourself for Heroin. If you choose wisely, you will probably be the dean of a prestigeous medical school, and have a trail of young'uns in short white coats, long white coats, and everything in between. You should stress yourself out about this as much as possible, and lose some hair and/or sleep over it. This has the secondary benefit of making you look older and deliberate, which patients dig.
Anka