Perhaps if I had more time, but in my experience as a battler I have never seen a successful team with Porygon-Z or Vaporeon as a lead :p
Yes. Perhaps I should explain:
Vaporeon should not be used as a lead, but only because it is almost entirely outclassed by Empoleon. Given that it has a powerful Surf/Hydro Pump, and quick attack, it can 2HKO every common lead bar Roserade, only allowing one turn of setup. Its only notable advantages over Empoleon are that it beats Infernape and can pass wish later, surviving with much more HP in general, but this is really nothing compared to SR. It's not a poor lead by any means, and I have tested it. (I also never got exploded on, thanks to either a 2HKO on Metagross or Protect with my sets)
There is a porygon-Z lead set currently in C+C, using Icy wind and download to good effect, although I have not tested that particular set. We will wait to see what quality control thinks of it.