Who is the strongest fusion, Gogeta super saiyan blue or Vegito super saiyan blue? Dragon Ball Super Broly shows,


   Gogeta defeating Broly


About Broly it is said


   He might be stronger than Beerus 


If you consider these facts alone you could think Gogeta is stronger than Vegito but, of course, you can think Goku and Vegeta got stronger since before the tournament of power to the time they fought Broly. How about other clues in the series, movies, manga, official guides about Vegito and Gogeta's strenght? Who is the strongest fusion, Gogeta super saiyan blue or Vegito super saiyan blue?
Based on your question, I believe you are comparing the Vegito from the Future Trunks arc and the Gogeta Blue from the Dragon Ball Super movie? Then yes! Gogeta Blue is definitely stronger. The reasons being, for one, Goku and Vegeta have gotten significantly stronger throughout the T.O.P, in comparison to the Future Trunks arc. Secondly, irrespective of whether Broly is stronger than Beerus, his power has been compared to a God of destruction. I do understand Shin made a comment in the manga about Vegito rivaling Beerus in the Future Trunks arc, however, I honestly am not going  to consider it simply on account of the number of inaccurate statements we have seen from Shin throughout the series(He thought SSJG Goku might defeat Beerus, SSJB Vegeta was winning against Jiren, Vegeta might lose against Pui Pui and the list goes on).Also in the anime, there is an alternate Corrupted version of Merged Zamasu who is significantly stronger. Beerus comments he'd be able to easily defeat Merged Zamasu(Who was going toe to toe with Vegito Blue). Jiren's power was compared to that of a G.O.D and Beerus being one of the strongest G.O.D's should rival Jiren(At least before he releases his dormant power) and Jiren even before he releases his dormant power, is in a way implied to be stronger than Vegito considering the fact that Goku and Vegeta didn't resort to fusion to challenge Jiren and it was heavily implied Goku would have to master UI to win.Now suppose we have an alternate reality where Goku and Vegeta fuse into Vegito instead of Gogeta in the movie, I believe Vegito would be stronger simply because the Potara Fusion has been stated to be more powerful. The Potara earrings are owned by the highest beings of the universe. The Supreme Kais and the traditional fusion dance was created by a bunch of mortals.