What are your thoughts, taking all of the manga evidence into consideration? How significant is the difference between Goku as he is now and Goku as he was in the Boo saga with all God transformations taken out of the picture? And why?
That's not what happened. Goku turned into a Super Saiyan God, one-shotted Trunks, then switched back before he noticed. You can see the sparkling SSG aura around his leg in the panel where Trunks gets hit, if you look carefully.
I would say by enough that current Base Goku is considerably stronger than Buu-Saga SSJ3 Goku. He's fought too many powerful enemies and received such good training up till this point.
Based on the last Manga Chapter, SSJG is still an assload more powerful than SSJ3, I don't think those gaps have changed by any means. the gap between SSJ2 and SSJ3 is still shown as considerably larger than the gap between SSJ and SSJ2.
"I was lying! See? There's an Omniverse in the box. And that Omniverse died. But alot of the lives in it carried onto the new one. New broom--same handle."
Example 1: Hit, who was stated to be less powerful than SSJ1 Goku by Beerus, was still on the same level as <10% SSJB Vegeta, and wasn't *completely* overwhelmed by SSG prior to powering up.
Example 2: Goku Black in base did a decent job of holding off SSJ2 Vegeta in base, but then still lost to him when he himself went SSJ2. Black's jump from post-zenkai SSJ2 to SSJ Rose also didn't seem that massive, honestly.
Example 3: When Goku fought Trunks, his SSJ forms were noted to be inferior to Trunks' by both Vegeta and Whis. While I agree he was probably holding back (although it makes Vegeta/Whis' comments weird), it's worth mentioning that Goku did resort to going SSG to finish the fight. If Goku was stronger than Trunks in base, and if the power gap from base to SSJ3 is as big as it was in the Boo saga, then he shouldn't have even needed to sneakily use God to one-shot Trunks. This is reinforced by pre-rose Black, who was comparable to current Goku/Vegeta (without SSG/SSB), who reached that level solely from fighting Trunks.
Examples 1 and 2 seemed to be pretty tame as far as I saw. Goku did far better as SSG then as as SSJ. And base Black fought Vegetta only briefly and was on the defensive the whole time. Plus, who knows, Black's SSJ forms may simply be weaker than Goku's. Either way, it's not nearly enough to suggest that Goku's forms have weakened IMO.
Well Goku's performance against Hit did seem to be drastically better when he went SSG. He went from losing to a borderline stomp. And like I said, Black's forms may simply not have the same multipliers as Goku's.