I've had insides, balconies and mini suites. Of course the mini suite is my favorite, but it cost more than the inside.
I typically spend a lot more time in my cabin when I have a balcony or mini suite. If I have an inside, I usually am in it just to rest or sleep and change clothes. The darkness really does help for those of us who have trouble sleeping and usually the insides on the lower decks are quieter, with less foot traffic and you notice less motion, if you prone to sea sickness, this can make things much more pleasant.
I am very happy to cruise in pretty much any category cabin. The balcony is nice to have but I won't pay an arm and a leg for it.