From the Zappa I've listened to - which isn't a lot, but some - I get the impression that he was trying too hard to be "weird," "difficult," or "quirky." It's the difference between your average CRI LP (not counting the Feldman, Partch, etc. titles) and, say, Xenakis. Xenakis didn't have to try!
Of course, I can't fade FZ completely because he was good for foisting more Beefheart on the world, but... as a composer, he's totally uninteresting to me. Alan Silva is sometimes quite interesting (not always). I'm not comparing the two, really, but you get my drift. I was merely stating that I was curious to hear Zappa the guitarist (who's decent) in the historical context of the Actuel festival.