I think this has been broought up a few times in older threads (like before I even joined this site kinda old).
From what I can remember from the discussions, the cholestoerol 'tail' of the PC molecule makes it difficult to penetrate the skin. The idea of Alpha-GPC (PC without this 'tail') was brought up; however, I think it is needed to provide the fat-destroying effects.
Lastly, Lipoderm (if you look at the ingredients list) contains lecithin, which is essentially PC.