I love two contradicting arguments being used for the same purpose, feels like I don't even need to do anything to debunk them. "Exhausted his power" is your headcanon
He was not tired,
And SSJ consistently has not shown this horrible level of stamina you just made up.
Although you're free to make a whole CRT to include this easily drainable stamina to the profiles though.
Both can't be true. Either he was initially at full power and then dropped, or he never was. The latter implies Cabba's SSJ is stronger of all things.
Rage serves as a way for characters (specifically saiyans) to exhibit higher levels of power than they are normally capable of. Cabba was already beaten badly then went Super Saiyan and was able to surpass Vegeta, as stated by Piccolo. In that scene we see him punching and blasting relentlessly, both actions being incredibly exhausting and even though Cabba was clearly still enraged, Vegeta ended up taking his last punch with no issue. That's after Vegeta's knees were shown buckling, Cabba overpowering his guard at one point and Vegeta even needing to defend at all.
You're claiming that, what? Vegeta was holding back that entire time? Well I'm afraid that doesn't align with the narrative. We have the writers depicting a character specifically state Cabba was overpowering Vegeta and we have them depict Cabba exhausting his power on attacking him relentlessly, evident in what Cabba is doing. It's never stated or shown that Vegeta was holding back.
And as for Super Saiyan being straining on the body? Already
cited earlier. By Tien, Piccolo and even Vegeta. Three characters backing up the idea that Super Saiyan is incredibly straining to maintain in a single page.
Cabba was already injured, meaning it took more energy to do anything due to the injuries, so his power came from rage. He, due to rage, punched, kicked and blasted with all his might exhausting his reserves and, despite initially being significantly stronger, ended up unable to even phase Vegeta despite still rage boosting because he exhausted his energy earlier via Super Saiyan + Inefficient rage-based attacks.
Point being, there's no way in hell Cabba vs Vegeta can be used for scaling MSS1 and SS1. There's too many factors involved (Injury, energy waste, Super Saiyan being straining, rage-boosted power) to actually determine how similar their powers are. The most we have is that a Rage-boosted SS1 is superior to an MSS1 in raw power. That's it.
