Goku and Vegeta use Fusion techniques surprisingly often in Dragon Ball Super for two people who claim to hate it so much. The non-canon promotional anime Super Dragon Ball Heroes has seen the mighty Saiyans cast aside their disdain for the ability entirely, frequently opting to Fuse to take on powerful foes without a moment's hesitation. The frequent appearances of Vegito and Gogeta in the promotional series have re-ignited the age-old debates about the superior Fusion.
Super Dragon Ball Heroes' conflict spans the entire multiverse and even alternate timelines, with Goku and Vegeta frequently partnering up with Xeno Goku and Xeno Vegeta, their Time Patrol counterparts. Xeno Goku and Xeno Vegeta use Dragon Ball GT's Super Saiyan 4 transformation rather than DBS' Super Saiyan Blue, resulting in the debut of SS4 Xeno Vegito. With a new Goku/Vegeta Fusion on the table, let's look at SS4 Xeno Vegito and SSB Gogeta to decide which of these Fusions is more powerful.
SSJ4 Xeno Vegito Still Has the Potara Earring Weakness
The Xeno versions of Goku and Vegeta in Super Dragon Ball Heroes are full-fledged partners as members of the Time Patrol. Guarding the flow of time against those who would meddle with it, the two Saiyan warriors often use the iconic Super Saiyan 4 form from GT. These counterparts to the original Goku and Vegeta don't hesitate to use Fusion if that's what it takes to defeat their enemies. The pair predominantly use the Potara Earrings of the Supreme Kai in order to Fuse into Vegito.
SS4 Xeno Vegito has made a handful of appearances scattered across SDBH, facing off against villains such as the evil Saiyan Cumber and even Broly, who uses a new transformation dubbed Super Saiyan 4 Limit Breaker. Xeno Vegito defeated Cumber while the evil Saiyan used Super Saiyan 3, but only managed to hold his ground against Broly before getting an assist from the main timeline's Vegito.
While SS4 Xeno Vegito is certainly a force to be reckoned with, he is just as limited by the notoriously frail Potara Earrings as previous incarnations of Vegito. Even though Potara Fusion is meant to last an hour, Xeno Vegito never makes it anywhere close to his time limit. While there's never been any reason to believe that either Vegito or Gogeta are inherently stronger than their counterpart, Vegito's inability to exist for more than a few minutes puts him at a severe disadvantage when compared to Gogeta.
Super Saiyan Blue Gogeta is the Pinnacle of Goku's and Vegeta's Fusions
Born of the Metamoran Fusion Dance, Super Saiyan Blue Gogeta is the superior Fusion simply because of the Fusion Dance's better track record of stability. The full 30-minute time limit is almost always reached with this method, the only instance of premature separation being when one of the participants was weaker than the other, resulting in an unbalanced Fusion. SSB Gogeta's sole (canon) appearance was his battle against Broly, where he easily defeated the Legendary Super Saiyan without fear of splitting too early.
Unlike most comparisons between Goku's and Vegeta's Fusions, this one has merit to the idea that SSB Gogeta may indeed be more powerful than SS4 Xeno Vegito. Super Saiyan Blue uses god power while Super Saiyan 4 is just another Saiyan transformation. While SDBH did contain an SSB vs SS4 fight, it was a brief scuffle where the two Gokus used less than their full power. But it seems only logical to say that the Goku wielding god power would have emerged victorious in a full-on battle.
Even if the gap in power between SSB and SS4 is minimal, SSB Gogeta would likely still be able to defeat SS4 Xeno Vegito simply by outlasting him. Gogeta's power in the film Dragon Ball Super: Broly punched a hole into another dimension. Xeno Vegito's power, while impressive, has never been quite so cataclysmic. So, is SSB Gogeta more powerful than SS4 Xeno Vegito? Probably. Could he beat him in a fight? Most likely. Will that ever happen? Doubt it.