First let me say that I don't have a pull type. But I will give my opinion anyway. /forums/images/graemlins/grin.gif There are 2 pull type configurations. One has wheels mounted at the rear of the deck. The other has the wheels mounted mid deck. Both pull like a trailer.
The main advantage is that it will follow the contour of the ground instead of rising and falling as the tractor goes over bumps and dips. That should give a more even cut over uneven ground. The mid wheel mount should be the least likely to scalp.
The main disadvantage would be that backing up would be like backing a trailer, much more time consuming than a 3 pt.