I would say the major difference is that while MSNBC is absolutely full of left wing bias, their pundits are much more clear about what is their actual opinion and what is part of the actual story. On Fox News they often present biased information and opinions as actual news or so mixed in it is difficult to distinguish.
If you only received information from MSNBC, you're likely be a rapid liberal who thinks all Republicans are witch burning racists who want to bring back feudalism. If you watch even a segment of Fox News without understanding its bias however, you're likely to think that whatever democrat they happen to be talking about is evil, incompetent and on drugs.