In the anime and manga they kept hinting that Sasori is stronger than Deidara. Deidara even says it himself. Since I don’t think he was lieing I think he underestimated himself and overestimated Sasori. Deidara could definately beat Sasori. All he needs is some tough C3 clay and Sasori is lost. I do think it would be a very long hard fought battle. If it’s outside in a very big plain than it would be a lot easier. Deidara wins.
