One of the major themes of the Kamigawa world is the war between the spirits and the humanoids. The spirits wield their arcane magic, while the Samurai, Snakes, Foxfolk, and Moonfolk fight against them through more conventional means. The Rend Flesh and Rend Spirit cycle nicely captures the feel of the war, with each side getting a way to cut down a soldier of the other side. Rend Flesh, being spirit magic, is of course Arcane, while Rend Spirit, being the magic of the "fleshy" (as I like to call them) creatures, is just a straightforward instant.
I hung out in the new Pro Tour Player Lounge for awhile (and trust me, it's nice!) and asked some players about which card they'd rather have for their deck. Many of them weren't even entirely sure, despite the format having existed for four months, but with minor prodding everyone came to one conclusion or another.
Rich Hoaen gave the nod to Rend Flesh, citing the potential to splice as his reasoning. Adam Horvath agreed with him, saying that he believes Rend Flesh to be the better card "unless there are a lot of Spirit bombs like the Dragons or Hikari in your draft." Osyp Lebedowicz had a different reason for liking Flesh. "It just kills the good creatures: Nagao, Meloku, Blademaster, etc." Mattias Jorstedt, when asked, was on the side of Rend Flesh, but then wavered, saying, "Well, I'm not sure…I had it today and it was awful."
So who defended Rend Spirit? Antonino De Rosa was first to jump to the cause, saying, "Flesh kills the bombs, but Spirit kills the solid commons, which is more important." Jeroen Remie was on the same page, adding, "It kills more scary commons like Moss Kami and Kabuto Moth…most Flesh targets are uncommon or rare."
Finally, rising star Tim Aten said, "In the beginning everyone liked Flesh better because it's Arcane but that's just stupid…it's really close but I guess I like Spirit better. It kills creatures you have to get rid of, like Teller of Tales and Kabuto Moth."
Who would have thought there'd be a format where a card that says "Destroy target Spirit" and a card that says "Destroy target non-Spirit" end up being roughly equal?
Welcome to crazy world.