It can go either way. It's definitely not a stomp for Deidara, since Kakashi is basically a Sasuke without CS2 who Deidara lost to, but Deidara doesn't have the privilege of Tobi planting his mines this time, which removes immense pressure from Kakashi. It'll come down to whether or not Kakashi will get to Deidara before he summons and flies up on his clay dragon/bird, or simply destroy it. If he manages that, then he can win by pressuring him in CQC with clones and his ninja hounds. If Deidara flies up, though, there's not much Kakashi can do.
I'll give this to Kakashi, high difficulty.