Yes, the Pros are noticeably heavier, but it's not as bad as it seems. They are very evenly weighted, so it's not like some laptops where the side with the battery is about 3X heavier than the rest of the thing combined. So if you get yourself a backpack with a padded compartment, you will almost certainly be more annoyed by your books shifting around.
And since you talk about Euros... 2.4 pounds is approximately 1 kilogram, and 5.6 pounds is approximately 2.5 kilograms. That's just a quick and dirty conversion, but should be within 0.1kg in both cases.
Oh, and the MBP has the addition of a FW800 port, which may come in handy some day, you never know.