PEP66- Larger fin area, fan orientented for slocket usage (i.e. fan officially sits on the side of the HS) However this can be modded so it sits up straight or as someone did stuck two fans one sucking the other blowing. There was an article on the front page about it (before xmas?).
PAL6035- Smaller sink, fan orientation the traditional way- ie sitting square on top of the sink.
The PEP is the better 'Sink, as it's larger and naturally has a bigger surface area.