In one corner…Tainted Strike. A formidable game-ender I remember fondly from my Scars of Mirrodin prerelease game. (Yes, all the way back then!)
Until Scars of Mirrodin came out, the most powerful poison-counter creature available was arguably Swamp Mosquito (because of flying). Highest poison counters delivered at one time was whoever you attached Snake Cult Initiation to. Then infect came out and you could staple poison on anything for super-powerful killing potential. In a normal game of Magic, infect is not much better than normal damage, unless you build your entire deck around it.
But when we move to Commander (aka EDH) poison warrants some serious discussion. Have you had the talk with your Magic group? There's nothing in the Commander rules about poison counters, so the default rules are the original magic rules…10 counters and the infected player loses. This equates to some QUAD-damage to any player unlucky enough to get hit.
In the other corner…Exsanguinate! A formidable game ender I remember fondly from my Scars of Mirrodin prerelease event. (Is there an echo?)
A fiendish cross between Drain Life and Syphon Soul. Ramps pretty well in multi-colored decks since it uses any color mana to fuel the X. With enough mana, Exsanguinate can hopefully slug out the whole table, leaving you with a fairly arbitrary life total (because everyone else has zero).
Here are the points I have come up with so far:
1) Tainted Strike is much easier to deploy, casting at instant speed with only 1 mana.
2) The downside is that you need a sufficiently large creature to cause 9 damage on its own. Because you can't count on any other sources of poison to show up to the table.
3) The upside to Exsanguinate is that it creates a bigger life swing between you and your competitors. And while it doesn't kill any one particular player any faster, if people have been playing well it will probably kill the weakest among them.
4) The life gain is significant. In a 4 person game, a 7 mana Exsanginate would gain you 15 life, practically another turn of damage, unless things haven gone truly…terribly…against you. But I like to see more of a 15 mana Exsanginate, draining 13 from each and netting 39 life. You can't go wrong with that.
Right now, my gut is leaning toward Exsanguinate. The last couple games I played saw a substantial increase in board wipe. Bigger creatures either win the game on their own or perish a quick and fairly unavoidable death. Plus there is a hidden cost to playing Tainted Strike with successful, ultra-poisonous results. Your group is bound to make some sort of house rule (usually while you are in the bathroom) raising the poison limit to some more reasonable figure like 15 or even 20. I'm sure there are many Skithiryx players out there who know this scenario well.
If you have any input yea or nay for either card, please let me know. I received a lot of feedback (including 1 phone call!) over my last fight between Eternity Vessel and Mindslaver. The response was mostly that I was completely nuts for picking the Slaver. Perhaps I'll have to do a mailbag with reader responses for these types of things.
Thanks for reading!