Originally Posted by
Vandalize
This is a point that has been bashed over and over in this thread. But here we go again:
If you're able to Dread Return Griselbrand, you'll dredge your whole deck (leaving a few cards not to lose on your next draw step). If you do dredge your whole deck, you'll hit every Bridge from Below, as well as every Cabal Therapy. If you throw 4 Cabal Therapies at your opponent, and make lots of zombies, what are the odds they'll make a come back? Moreover, Griselbrand is a huge threat by his own, as a 7/7 flyer lifelinker.
In order to win with Flame-kin Zealot, you need at least 2 Bridge from Below in your graveyard, and at least 3 bodies to sacrifice for Dread Return (assuming your opponent has no blockers, etc...). So, to deal 21 damage, you'll need 6 zombies + FKZ, which is only achieveable with fast starts (against any competitive deck, at least).
Resuming: Griselbrand gives you 99% chance to win next turn, while FKZ gives you more or less 50% to win in the same turn (those percentages aren't math based, just a random throw). My bet is on Griselbrand.