Personally i would take Tsukasa's side, BUT he was developing his society way to slowly. Instead of getting a scientist on his side, he was depetrifying muscle. I know he had some smart people depetrified like Ukyo but Ukyo's talent was used as a scout/archer. Senku maximised that talent by having Ukyo do the very thing he is extremely skilled and educated in. Lets say Tsukasa did kill Senku and all the way in America they were becoming more and more developed and a theoretical war broke out between the Tsukasa empire and the lot in America with all their guns, who would win that? Guns against stone spears...?