Warning: Contains spoilers for Dragon Ball Super Chapter 84
Since the two first met in Dragon Ball's Saiyan Saga, Goku and Vegeta have had a contentious relationship to say the least. Vegeta has been outpaced by Goku several times throughout the series and has fought desperately to keep up, which may have led him to actually surpass the Saiyan in recent times.
Goku and Vegeta first met in Dragon Ball Chapter 223, titled "Piccolo's Last Stand." Only a few chapters later did their long-awaited battle finally begin, with Vegeta having a clear upper hand. Goku was only able to keep up with Vegeta at the time by using the Kaioken, a dangerous technique which allowed for Goku's ki to be amplified at the cost of extreme strain to his body. This relationship began to change in the Frieza Saga where Goku began to accept more of his Saiyan nature. Dragon Ball was clearly demonstrating that the acceptance of one's own nature contributes to building strength. Vegeta has been trying to catch up to Goku since the Saiyan Saga, pushing his base forms to greater heights, especially in the context of Dragon Ball Super when the Kaioken makes its return. This power and desire has culminated in Vegeta being able to reproduce the same kind of strength as Goku, even without the use of the Kaioken, and Dragon Ball Super chapter 84's revelation has finally given him the opportunity to truly accept himself and enter the same realm of growth Goku once did.
In the battle with Gas, both Vegeta and Goku are shown standing side by side as they assume the states of Ultra Ego and Mastered Ultra Instinct, respectively. This is particularly interesting because it depicts both Goku and Vegeta as equals, at least in their current forms. The last time a pose like this was struck was during the Tournament of Power where Goku and Vegeta utilized Super Saiyan Blue Kaioken x20 and Super Saiyan Blue Evolved to stand a chance against Jiren. This was also meant to imply that Goku and Vegeta in those forms were equals. That being said, depending on the multiplier for Super Saiyan Blue Evolved, this would mean that Vegeta should logically have a much stronger base form since the Kaio-ken is treated as an “unnatural" multiplier with severe ramifications if maintained for too long. Chapter 84 by Akira Toriyama is a very similar case in which Vegeta’s Ultra Ego (despite having much less training time and mastery over it) is being held to the same kind of pedestal as Goku’s Mastered Ultra Instinct.
Though it’s been made clear that there are various levels of Ultra Instinct, it’s currently unknown if the exact same applies to Ultra Ego. Unlike Ultra Instinct, Ultra Ego was never referred to as an “omen” or “sign” the way Goku’s incomplete form of Ultra Instinct was. Despite this, there is depth and mastery that needs to be achieved with any technique and Vegeta’s Ultra Ego should be no different. So far he has put up a much better showing than Goku in the battles with Granolah and Gas. Because of this it seems plainly evident that Vegeta has a base form leagues beyond Goku at the moment. Constantly having to close the gap between Goku's Kaioken x20 technique in Dragon Ball Super forced Vegeta to become practically 20x stronger, if not more, on his own terms.
Goku’s Mastered Ultra Instinct may be powerful but Vegeta’s ferocity and staggering durability in Ultra Ego seems to be giving him an edge when it comes to combat. As Vegeta himself said, strength rankings are constantly changing, and now it seems as though Dragon Ball Super is pushing Vegeta towards the top.
Dragon Ball Super Chapter 84 is available on Viz's website.