4 speed or 4 speed OD?

Rockerdude said

..Or you could fork out the cash and go with a 5 speed. Best of both worlds.

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Help me understand what two worlds that is. Since the Mopar OD unit has a 3.09 1st and a .69 OD, it already would seem you have the best of both worlds. Who needs to spend 3K bucks for one more gear?