Deidara confirmed that Sasori was stronger himself, same way Kisame said Itachi was stronger than himself too. Sasori was capable of somehow killing the strongest Kazekage before Gaara so Sasori being stronger than Deidara is believable, Deidara has no reason to make that up.
I suppose. But just for the sake of debate, what could Sasori do against Deidara when he is up in the air flying on that clay dragon? And are we counting C0 in this fight, because they both die technically, but I'm not sure if Sasori has a way to evade it, like how Sasuke did.
Could Sasori live through C4? On one hand, he is a puppet, so it might not work on him since he may not have a bloodstream to impact, but on the other hand, he still has a heart of sorts. The technique could disintegrate his heart and kill him, so in a way, Deidara has his own explosive poison to use.