There is no single "best" broker. Things you should look for include fees and commissions and service for the type of investing you intend to do. I think you need to determine what you are looking for in a broker.
A better place for your question would be on the Discount Brokers message board at http://boards.fool.com/Messages.asp?mid=27268783&bid=100...
There is also a Full Service Broker board at http://boards.fool.com/Messages.asp?mid=27104846&bid=100... but, that board doesn't get a lot of traffic since most Fools prefer discount brokers.
I suggest you read that board's FAQ and review a few weeks worth of postings there.
I am not familiar with Morgan Keegan, but, generally brokers working through a bank is not too great for a beginning investor. There are some exceptions, however.

Bob