OK so maybe I was a bit too excited before so let me try again:
The reason its great to have two games is because these are not STATIC games, they change as you play with a certain group of people, and would change a different way if you played with another group of people (12-24 game sessions, each one unique to your choices from the previous) BUT once you start one campaign you CANNOT go back, so your stuck with your own personal changes. Having another board means you can play the WHOLE ENTIRE campaign twice , and most likely with two different groups of people, now this does not need to happen at the same time, you might finish the campaign once with your group of friends and forget about it for awhile, then you find 3 other people that like pandemic and want to play, you have the ability to play from scratch rather than replay the endgame scenario from your other completed campaign, I cant say anything to value for a US consumer but from a Canadian standpoint the price is really good.
Do some research on this, I own a copy so this makes a lot more sense to me i guess. but this is the #1 rated overall game on board game geek and I think its staying there until season 2 comes out (it is in the works)
Also Red is the better of the two, Blue has chemistry errors on the box, a carbon molecule can only have a max of 4 bonds, not 5 or more :P