I would say the 251 neck is probably a bit better, even though it's lacking haste because it has a lot more spellpower. You already have a lot of haste (although I'd get the new totem when you can afford it). Alternatively you can stick with the Wyrmrest necklace until you can get your hands on that Gunship 25 neck. Having a lower ilvl neck might help you get it if your guild uses Loot Council.