Is the south river run more difficult then the north bridge run? Or are they pretty much the same?

South River is mostly flat with a mild gradient in some stretches especially noticeable on the way back. There is a short muddy, steep path that allows you to walk up to the Hudson river at the final stopping point. There are a couple of nice scenic points along the way. I have not visited the North segment.

Not sure which is north or south, but the way out is slightly steeper, but neither way is difficult.