Kurushimi

If they fought in the desert, Gaara would have plenty of sand to both attack and defend. He could even protect both himself and Kakashi if it was to come to that. Still, I'd say the the C2 Dragon's missiles would be able to get passed Gaara's sand, seeing as CS2 Saskue (who was stated to have incredible speed at base) couldn't dodge them completely. On, the other hand, it couldn't be as manuverable as the Deidara's birds so he probably wouldn't be able dodge Gaara's sand attacks for long. Though, he might also be able to take out Gaara early on...

Also, Kakashi's genjutsu probably wouldn't work on Deidara, with they eye that he has developed. However, Kakashi has a lightning affinity and I have no doubt in his ability to figure out that the lightning could deactivate the bombs. He'd also be able to see C4 Garuda's spores but I doubt that he'd be able to do anything to stop them. Gaara however, could wrap himself in an sand sphere, and survive the attack.

All in all....

I am undecided. =/
(Though, if they fought outside a desert, I'd give it to Deidara.)

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~ xkcd