Resolution definitely isn't the same - the new NavPro is widescreen!
Its 1280 x 640 compared to the previous 8" 800 x 480.
In terms of desktop computers, the difference in powering that is nothing, but the computer in your car is not a desktop PC running the latest top end Intel processor, its the smallest processor that they can get away with.
When you have the map on the AID, you can have a different view to the one on the MIB as well - so it is actually generating twice the output too.
Its really hard to find the actual manufacturer of the MIB unit and read their tech specs sadly.