When Goku powered down to an SSJ during the fight with Beerus, Beerus said his power hadn’t gone down from SSJG, but even so it’s obvious that SSJB is a more powerful form. He never powers up to SSJ against anyone who beats him as an SSJB, and Vegeta even powers up from SSJ to SSJB against Cabba. And all that’s not even counting the fact that Goku flat-out told Frieza the blue form was stronger.
Even worse, in the manga only, Goku and Vegeta can both still use SSJG, and they power up from SSJG to SSJB multiple times! And for the final nail in the coffin, both Dragon Ball Heroes and Dragon Ball Xenoverse have higher stats for SSJB than SSJG. While neither of those last two are remotely canon, with all the other evidence it’s obvious what’s being implied here.
You might say that SSJG forced Beerus to fight at 70% power, but here’s the thing: that was only stated in the movie, not the anime that replaced it. Therefore, it’s not canon anymore, and it can’t be used in an argument. The only percentage we get in the anime is Beerus saying he used 100% power, and that was stated to be a lie.