Hiku said: If that form is stronger than SSG, then that is probably how it works. But I'm not sure if the form itself is stronger than SSG, or that Goku and Vegeta trained themselves to be strong enough to be able to beat Beerus together. (I can't recall if Whis was refering to 70% Beerus as he was in the fight with Goku, or Beerus at 100% when he said that.) Either way, it's hard to measure just how strong two people need to be in order to combined be able to beat a stronger opponent. Goku might have gone through Zenkai after his fight with Beerus in the first film. And after that, (between the end of the first movie and beginning of the second) Whis could have granted Goku and Vegeta the experience a few times while training to increase their battle capabilities. |
Oh, now that you mention it, I remember the good old power levels. They screwed it badly around Frieza because the official power levels mean, besides the 50x super sayan multiplier, absurdly high 10-25x Zenkais for Goku and Vegeta after the Ginyu force, and a similar power level increase for Piccolo between Frieza and the Androids. And then Shonen/Toriyama went on to say "it was to show numbers don't matter" to try to fix it...
As for Vegetto, on this week's episode, after being beaten badly, Goku mentions he thinks even Vegetto couldn't beat Beerus. That's an interesting note, but it remains to be known if Goku is referring to the ascended SS Vegetto which beat Buu Gohan, or an hypotethical SS3 Vegetto. According to the charts I did once for my own amusement (hah) trying to fix the inconsistences since the Ginyu Force, SSJ3 Vegetto would be exactly 90% of Beerus.