I would echo Dave's comments. He has much better ears than me, but I would say that the v3 just has a rounder, fuller, livelier sound in the crucial area most of us play in. Punchier would be a another was of saying it? Certainly more pleasing to my ears.
I'm glad I went and let Dave play. So much easier to have another player so I could listen objectively. And yes, the older unit is louder.
Oh, and don't play the Nord Piano 3. The damn thing is lovely.....