Hmm, none of the PoP planes really "stand out" to me. They all have their one or two high points, but I've always thought PoP was where SOE really started to lose creativity and start pumping out carbon-copy clones of zones.
If I were to pick from the choices given, I'd have to say HoH, because I like brightly lit zones - it's harder to hide bad graphics in brightly lit zones, or PoJ, because I liked the whole "7 trial" idea.
--Nik, who plays on a server that HAS Plane of Mischief v1.0, Al'Kabor. :D