We just had a deck 6 inside cabin on Eurodam, and i have to say this is the best (most spacious) inside cabin I've ever had!
We always book inside. Of course, I'd take an outside or balcony if it was offered for free.
We like inside for the following reasons:
-total blackout - I get the most amazing sleeps this way
-we don't "stay" in our cabin other than to sleep
-I'm not claustrophobic
-We like the price savings. Even though an outside is sometimes only 10 ore more dollars per night, I sill prefer to save teh $70 overall and spend it on something else.
Our next cruise is on Disney, and we have the "magical porthole".
We haven't yet sailed Oasis or Allure though i'm anxious to try it. ... and that might be our first "pay for a view". I don't think I'd want to be be opennign up to all that interior noise with an interior view. Its the same reason I will never stay in a pyramid view at the Luxor in Vegas.