Originally Posted by
Obfuscate Freely
Parasitic Strix is interesting because, like Spike Feeder, it can be used both to gain infinite life and to kill the opponent. This alone sets it apart from suboptimal cards like Ghitu Slinger and Essence Warden.
However, I'm not sure that Strix is better than Feeder. The latter seems like a much better card to draw before Aluren resolves, and you don't have to protect it from Swords to Plowshares (since it can always kill itself).
It's also worth mentioning that Strix' trigger targets, so a Runed Halo or Solitary Confinement stops it. With Spike Feeder, these cards are largely irrelevant (Halo almost completely so) once Aluren lands, because you can gain life, draw your deck, and remove them at your leisure. However, with Strix, an untargetable opponent will prevent you from gaining life, which limits your ability to dig for (and protect) your removal for the enchantments.
There are some important potential benefits to running Parasitic Strix, though. The obvious one is that Aluren, Cavern Harpy, and Strix combine to win immediately, without needing any Raven Familiars, Man-o-Wars, or Walls of Roots. Thus, you can occasionally win games by just drawing that combination of cards, when drawing Spike Feeder instead might do nothing.
The other big advantage to Strix is that Wall of Roots and Man-o-War don't have to be in the deck at all. I'm not saying that cutting either of them is necessarily correct, but I have tested builds of the deck with only a single copy of Wall, and that single copy was only there because it had to be for Spike Feeder to work.