Well, I have both of them (access to the Lightborn, at least), and I'm having trouble deciding which I should use for what...I'm double feral specced kitty and bear, I'm just not sure how much of an increase I'll see in either specs with having both weapons. I would use the Spire for tanking, with mongoose and Twin's Pact for kitty, with berserking. I'm not much of a theory crafter so I'd rather just see what peoples opinions are.
I'm using Lightborn Spire for both right now until the 258 version of Lupine Longstaff (or something in ICC with arp) drops. The lack of expertise on my current gear made me swap the 245 Lupine Longstaff for Spire.