Jenny,
Navigator veranda rooms are in the back of the ship and have a full veranda , but with a metal bottom and an open porthole opening. The opening is larger on the Wonder than on the Magic and you can see pictures if you go to Barb's site. The other difference is that instead of two chairs and a small table you get a padded bench, padded chair and a slightly larger table. Many people would call the view obstructed but DH and I (who have sailed with a regular veranda on our first two cruises) tried on Navigator's veranda on our May Wonder cruise and loved it so much that we booked one for our Magic cruise next May.
Another nice perk of these rooms is that since you are in the back of the ship your muster station for the emergency drill is in Animator's Pallate instead of out on the hot deck!
An Oceanview room has no veranda, but a very large parthole (unless you are on deck 1 then you will have 2 small ones). Again pictures can be found on Barb's site.
Hope this helps!