It has been my experience that the flexible black piping has not held up as good as plain old PVC for me over years.
That is what I have been told as well. It just sure would be a lot easier up front to use that stuff as I would be able to bend it gently around trees / rocky soil, and it would contour with the slopes of my land better than regular PVC.
...but I don't want to have to replace it all and try to find a leak in the 600 feet of it sometime either! Thanks for the reply!