Well, it is really a matter of personal opinion and finances, as well as how much you think you'll be in the cabin. If you have a child that naps, you might find you are in there more than most people. Then, it would be nice to have. They are a good bit more expensive though, so don't worry a bit about the fun you can have in a cabin with no verandah. The ship is fun whatever room you choose!
I personally would love the verandah for sailing into ports and really getting to watch the islands as we approach. But, we are a party of 5 and require 2 rooms. I won't get a verandah because I won't allow my children in a room with one when I'm not directly with them.
Many people report they are not in the room much, so on a 3 or 4 night cruise, it might not get used as much as a 7 night.
It is probably a call most often made based on personal finances more than anything else.
Good luck!