Big advantage
If you have a DH+ network, you can access any node on the network from one location. I have one 504 that is in a Class I, Div I. area, inside a Nema 7 enclosure, (one of those really thick ones with a zillion bolts), by going on line from another node, I don't have to worry about the explosive atmosphere, or all those bolts.
Plus DH+ is faster than serial.
However, on the negative side, you can download the wrong program to the wrong processor, or make changes on the wrong node.