Confusing and fragmented in true open source fashion.
As far as I can tell Purr Data is Pd l2ork version 2.0 which basically is Pd l2ork version 1.0 with a new "Node Webkit" based cross platform UI. Pd l2ork 1.0 is still around. It uses the old tcl/tk UI library which Pd vanilla uses. Some stuff in 1.0 is not possible to use in 2.0 yet.
I was worried the performance of Purr Data would be horrible since other web based desktop apps I sometimes use (namely Atom editor) is horrible. Purr Data turns out to work well on my Thinkpad (running Windows 10).
Unlimited undo and zoomable windows means a whole lot to me. Some minor useful editing improvements are great. I hate the curved wires, though.
Patches saved with Purr Data is AFAIK backwards compatible with Pd vanilla, so it feels more like a new skin over Pd vanilla which is exactly what I want.