Obviously, if a person is close enough to drive to Ft Lauderdale then the $400 credit is a worthwhile difference, but if you are talking about Europe (and you live in Florida) and it is still just $400 credit, then it is not worth giving up the included air.
Now - I don't know if Europe is still just a $400 credit - it could be a lot more.
I guess this isn't rocket science - either the air or the credit is a better deal. You just have to go Expedia and see what the air is going for right now.