While HDPE might be superior(I personally don’t see any groundbreaking upside to it), the bottom line is pvc serves the exact same purposes as HDPE at a cheaper price. Both materials insulate, hold humidity, are easy to clean, easy to work with, and light. I had a Proline cage too and I personally was not impressed. I won’t go into details but I sold it and switched everything over to AP cages. And Ed actually lived about 3 hours from me.
In my opinion, if you go HDPE, make sure you use thick enough material so you have no flex. That was a huge negative on Proline to me. I could literally twist the cage and cause it to shift. But anyways, like I said, I wish you the best on success. Do what you love and you will never fail at it.