VampireWicked said:
But you see, similar Aura yet slender muscular build.
That was just in that (and maybe some other) panels. In other panels Vegeta and Trunks were already considerably less bulky:
It's possible that their armor made them look considerably bulkier in some panels as well. Either that, or Akira Toriyama's art wasn't entirely consistent in those panels.
Anyway, even as FPSSJ, Goku doesn't look less bulk than he did as a simple SSJ:
His aura and psyque looked just about the same in those panels.
The grade 2 and 3 transformations are the ones whose traits are a bulkier psyque and sharper aura.
When Goku got sick Vegeta as a SuperSaiyan was stronger. So scaling power wise at that point Vegeta's base was stronger.
That was before the RoSaT. There's no reason the same should apply to their post training selves. It just means that Goku's boost while in the RoSaT was way bigger than Vegeta's. According to the SEG, the "mastering the SSJ" route of training grants a more considerable boost to whoever is going through this route of training. But that doesn't mean its boost would be even remotely comparable to the Grade 3's one, it just means such route of training would be the more efficient one.
I absolutely agree with that, but it would also be pointless if there's only speed with no power to back you in combat. So both was needed.
Hence why Goku's full power SSJ should be right up there for him to stand a chance, since flashing the grade 3 transformation wouldn't do him any good due to its speed disadvantages. "All the power in the World won't do you any good if you can't hit the opponent". SSJ won't prevent you from getting your ass kicked if the opponent's power is way above yours, sure, but that still doesn't change the fact that flashing the grade 3 there would be simply useless. Cell, upon seeing how his natural power didn't match that of Gohan's, ascended to the Grade 3 level, and Trunks knew immeaditely he was commiting the same mistake to which he mocked Trunks earlier:
And Trunks, much like Goku and Cell earlier, was once again shedding light onto the fact that speed is the form's problem. It maximizes power, but it kills speed due to the excessive muscular mass:
And then the regular SSJ is best due to the lack of those disadvantages in which strength wasn't one of them. Goku says that they'd work on the SSJ, but not by maximizing its strength, but by getting rid of that instability and restless feeling, that is, they would work on the SSJ so they could feel as natural as possible when using that form, which was why Vegeta didn't notice the SSJ feeling when Goku and Gohan were transformed when they exited the RoSaT:
So that's why the SSJ Gohan and Goku were using was improved compared to the standard one. Maybe, just maybe its boost might be comparable to the grade 2 one to explain why they still didn't flash it as it doesn't suffer from the speed issues, but the FPSSJ isn't required to be as strong as the Grade 3 form when it was made clear such form wouldn't be used again due to its speed disadvantages.
If that were true then Goku would not've trained Gohan towards AscendedSaiyan/SuperSaiyan 2.
I think the SSJ2 is like the correct way to utilize the SSJG3's power. Both are utilizing incredible power surpassing the standard SSJ, but in the SSJ2's case the speed complements the power output due to the lack of excessive muscle mass.