Ducted air SHOULD be quieter and have better air distribution, especially in a large unit. I say should because I don't know how well these systems are designed. The best way to tell if it's worth getting is to have both systems going and see for yourself.
And as Krazeehorse says, how often will you actually use it? Even if the ducted system is hands-down better, will you use it enough to justify the extra cost? Only you can answer that.
We have had both and the only advantage that we see is the fact that it is less noisy. If you want quiet, get an RV that has the basement type air like what Winnebago uses. The duct work that I have seen is not designed at all to balance air flow. It just dumps the air into a duct system that is the same size throughout. And in many systems, the ducts are put in and there is only one set, even when you have two air conditioners. They just tie in the second air conditioner if you choose to buy the second unit. They are clearly less efficient when running into the ducts. The owner's manual for our air conditioners states that you should precool the RV with it dumped into the room before you shift to the ducting. Also, ducting can collect moisture when in high humidity areas and then smell or even drip a small amount. On the other hand, it is quite a bit less noisy when running through the ducts because the air noise is not all in one spot and the extra duct-work slightly dissipates the sound. While we do prefer the ducted system, we would not pay a great deal for it. Air distribution is better, but it still puts much more through the outlets near the unit and only a little to the others.
You said a Wildwood "camper"? A camper is only about 12 feet long, so air distibution should not a problem. If there is a major cost difference, I'd save my money and install a power fan in the over head vent instead. That's just a personal opinion. :laugh: