The interior cabins are virtually all the same; I don't think you can single out a "best" or "worst". I think your guidline should be, "where do I plan to spend most of my time while onboard?"
If you plan to spend a lot of time around the pool and playing sports, then Lido Deck or Riviera Deck might suit you. On the other hand, if art auctions, the Casino, shows, card games, the library, classes and lectures are your thing, Dolphin Deck or Emerald might be for you. If you are looking for real economy, Plaza Deck is actually a very good location. Or, if you plan to do some of everything, Aloha, Baja or Caribe Decks would be a good compromise.
If you are considering a balcony, the same guidlines could apply. There are no bad balcony cabins; but if you would like a recommendation, I would suggest the Catagory BB Balcony Cabins on Caribe deck. All the balconies on Caribe Deck are larger than the other standard balcony cabins; and Catagory BB will save you a little money over Catagory AB. Or if you are lucky enough to snag one of the BB's aft, grab it!
Thanks for that Penny, are all these the same size or is there any in better locations and is there anywhere i can look at the location. Do they overhang or does anyone look down onto any of the balconys?
The deck plans are on-line. Here's the link. You can either enter the cabin number in the box or you can select the deck plans and look at the various decks. I've stayed on all the decks you've mentioned and really cannot remember anything about the balconies. As long as I'm on board, I'm happy. Hopefully, the deck plans will help you.
Three of the cabins you list are balcony cabins and one is an inside.
Of the four you list D734 is by far the best; in fact I'm surprised it is still available--the aft balconies usually go right away. The cabin is standard size but the balcony is much larger and completely covered; and you have a fantastic view of the wake.
C206 and C209 are also standard size, and the balconies are larger than the other standard cabins, and only partially covered. Either of these would be great.