I think both PoW and PoS have their place in the future.
PoW is useful in the startup phase to establish a sufficiently large
base of coins that can later be leveraged by PoS.

But as far as PoW go, Cuckoo Cycle has some very distinct advantages over hashcash-scrypt.

Both were designed not to be easily parallellizable. But computing a single scrypt is as demanding
on the prover as it is on the verifier, which means we cannot just make the prover's work harder
(i.e. use more memory) without also making life (too) hard on the verifier, i.e. every client.

Cuckoo cycle on the other hand has trivially verifiable proofs, while you can make the prover
use up to 14GB of memory and spend many minutes even at the lowest diffculty setting.