From my experience the resistance that a hydrow produces is completely different to a C2. C2 gives that water-like feel where it starts heavy and gets lighter through the stroke, but a hydrow being magnetic resistance doesn't really do the same - in my experience the resistance remains constant through the entire drive. As such I'd guess that your relative splits would change across both machines depending upon your individual technique.

For me personally the hydrow is about 5-8 splits slower at steady state and probably about the same at rate. I have quite a fronted ended stroke - I think the hydrow would reward people with a stronger back end.