I think all in all, Raditz and Yamcha are probably the same more or less and the Cultivars are slightly behind. That's all I'm willing to give credit to Yamcha for. Unless you think Yamcha increased his power when he super speeded behind the Cultivar, I don't see it.
P, Yamcha thought he could take down all of the Saibamen by himself. He'd be asking for a death sentence if he's bluffing. Even though Yamcha is probably talking about 1v1 matches, he would still eventually tire out at a less than 1.1x advantage even if accounting the Saibamen's intelligence.