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The firewire port. Also, the 13" Pro has the longer-life internal battery, a better screen, and the SD slot. The other MacBook Pro's have larger displays.
 
The firewire port. Also, the 13" Pro has the longer-life internal battery, a better screen, and the SD slot. The other MacBook Pro's have larger displays.

Slightly faster processors (MacBook offered 2.0/2.4, Pro is 2.26/2.53), and the Backlit keyboard is standard instead of only available on the more expensive machine.

They're not exactly the same, but they're very, very similar. :)
 
Macbook had a user access to the batter, and HD but just by flipping a latch.

The Pro requires you to unscrew the entire back cover.
 
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