scrypt-N is a misguided attempt at being ASIC-resistant.
It's quite possible to make ASICs that handle any scrypt-N
with N in the range (10..20), since one can feasibly fit 128MB
on a single chip.

At N=20 however, scrypt is already unusable for another reason,
namely that verification effort also scales exponentially with N
(a fact conveniently ignored by its proponents).

X11 is something of a joke. 11 hash functions that are each
designed to have efficient ASIC implementations, are still
very ASIC friendly in combination.

The claimed GPU benefits are due solely to suboptimal implementation.

I'm not particularly crazy about scrypt-n, I don't like how the n-factor scales and it is just a temporary reprieve from asics.  That said, it IS a temporary reprieve from asic. So, for us GPU miners, its a way to stay relevant for a little while longer.  I know the asic lovers will flame me, but CPU/GPU mining has its place in the life-cycle of a coin, and scrypt-n, for all its faults, ensures that for the time being.  I personally like x11 much better (yes, yes, I know its not asic resistant blah blah blah) than scrypt-n.  They're both stop gap measures though, so why not use the one that doesn't rape your GPUs and your electric bill?