DP allows you to paint right on the model. You can rotate the model around in 3d and paint right on it. You can paint 2d in DP if you want to, though.
It also has several different maps/channels that you can paint to and see a crude preview as you paint. For example, you can paint on the bump map right on the model as see it as you go.
One of the major selling points of DP is Projection Painting. UV maps can't always be perfect, so trying to take care of texture stretching in 2d can be a real pain. Projection Painting takes a lot of that pain away.
Another good thing is that you can paint right across UV seams no
prob. You might get some artifacting due to interpolation, but easy enough to take of compared to doing seams the hard way.