There isn't really a Corona node material - you can think of the node editor as just a different way of viewing all existing materials. No special material required. So there is no difference between a material created in the native C4D material system, and one created in the node system. And of course you can just drag and drop from the native system into the node editor to start viewing and working with that (perfectly ordinary) material in the node editor, no conversion or anything required.
The one thing that is new is the shared map, e.g. I have one Noise map and I can plug that into as many slots as I want, in as many materials as I want. Not only is this nice and easy to view, set up and understand in the node editor, but the new thing is that the one very same map is now in all those inputs for all those materials - adjust the one source map, and you are adjusting it for everything it is connected to (previously, with the native material editing system, I'd end up with separate noise maps in each connection, so if I wanted to change it in all the places equally, I had to manually edit each occurrence of that noise map, once for bump, once for diffuse, once for in another material, and so on).
However the node editor works in such a way that this is pretty much invisible anyway :) You just get what you would intuitively expect - one map, connected to as many places as you like, that you only have to adjust once at the source, even though there is under the hood a magical new Corona Shared Map in use.