i would choose the extra night... you can still enter/exit a park (just has to be the same park) to go back to the hotel and rest... you can still go to a resort for a character meal... you can still get all the disney magic w/out hopping... but an extra day... well, imo that speaks for itself... go for the extra day... and like another poster said, you just have to plan really well... my advice would be to do the parks you cannot bear to miss first because if you have really bad weather or someone comes down w/a tummy ache or something, you will have time to make up what you might miss, kwim? (i would hate to visit AK in the beginning of my trip and never get to MK!)
good luck!
OOOH! ANOTHER THOUGHT! P.S. if you don't have one yet, sign up for a disney visa, and maybe you can accumulate enough rewards to pay for the hopper option even after you've added the extra night!