^I don't know if C3 would do the job against A. Deidara would've been using other clay bombs before it so A, even being the knucklehead that he is, could've figured out lightning neutralizes the bombs. So he could just smash C3 with a lightninged fist before it hit the ground. Anyway, with A's speed I do believe he could outrun it. And imo it probably won't do too much damage to him anyway with lightning armor, even though it's weaker than his dad's.
I'd give this to A because though Deidara has the advantage of range he's screwed against a strong lightning user. Not even C4 has an effect. I'd say A has a better chance of hitting Deidara through a mistake on the artist's part or because some people say he can jump higher than most in second state like we've seen with Naruto, putting him in range of Deidara's bird or dragon. Sasuke could get up to that height, so A should be able to. Though this battle does drag on I'm sure, I don't think it would end in a stalemate.
Though Deidara has the suicide bomb I'm not even sure that would work either. He uses it as a last resort so A will have doubtless learned his weakness by then, but then again he doesn't even need to to punch Deidara like he always does people with a lightning fist and defuse him. I'd give this to A, with high dif of course.