Sokidan vs Fake Saiyans is way larger. The Saiyans barely defended themselves against it and wre unscathed. Raditz had to run away from it and put his palm up and was still pushed back a bit.
Plus Fake Saiyans are stronger than Raditz (I don't see why Kami would use them as a test if they weren't at least stronger than him), and I only have Yamcha about as strong as Goku was 400 and his Sokidan is far less powerful than Goku's Super KHH.