well, for me it's not that easy to say because although i own both dvds, i had lethal a lot longer of course, so i've practised the lethal flourishes for a long time now. anyway, as mentioned above, the trilogy is definetely easier to follow because of the different teaching style, when you want to learn a flourish from lethal, you have to watch it over and over just to understand what's actually going on before you can really start practicing, and even then you might have overlooked something, at least that's what i've experienced.
my advice would be to stick with the trilogy for now, and once you get a couple of flourishes right you can get lethal, but you can't handle both at the same time ;-)
as for my very personal opinion i totally love lethal because the flourishes are so smooth and have such a nice flow, especially when you get better, and i hate the trilogy because i just can't do that pandora b**ch :-(
PS: why are you trying to start with the hard flourishes? just start with mecka or the skater cut or something like that...