Before arguing this, I'd like to say that I am not trying to troll here and I'd likely just be playing devil's advocate here, since Vegetto >>> Gogeta seems already set on most people's mind. So, I hope that when offering some counter arguments, people don't see me as a troll.
First of all, Vegetto being considerably above Gogeta was something that I have believed since always and have even done a huge topic today presenting the arguments for Vegetto >> Gogeta, but when reading many topics about this tangent, I have ran into many counter arguments about such topic that I'd like to discuss with you guys. I don't want to sound like a contrarian person and I know I even admitted Gogeta was outclassed in power by Vegetto in the OP, but I'd still be interested in seeing what you guys think about some counter arguments for this matter, which then may be seen as me maybe defending a position that is in general not supported by people and even by the manga. Still though:
Regarding old Kaioshin's statement, here's what he said according to Herms:
Chapter: 501 (DBZ 307), P6.2-6
Context: Elder Kaioshin gives the Potara to Goku
Elder Kaioshin: “Here! Put this Potara on your left ear! [ ] Put the other one on Gohan’s ear. Just by doing that, you two will be able to merge together! Like with Fusion.”
Goku: “Huh! Re-really!?”
Elder Kaioshin: “Of course. And what’s more, the effect is greater than with Fusion! This has been the trump card treasure of the Kaioshins since long ago.”
He stated that the "effect" is greater than with Fusion... does it inherently mean Vegetto is stronger though? He stated that the "effect" is greater, and with the time limit being already outright regarded as a weakness (to the point Gotenks likely didn't defeat Boo once and for all because of it), a lack of time limit could be considered as a "greater effect", even though the wording didn't ouright state such. So, I'd say that Elder Kaioshin's wording seems to be kind of too vague here for us to denote a power difference between the two methods. He probably didn't mean "joining without the need to do the steps to fuse" as a greater effect considering the Potara was introducced due to this weakness and he just explained Goku how he could fuse instantly with Gohan just by putting the earing on opposing ears, and the "greater effect" was treated merely as a bonus... but I'd still argue it's a bit uncertain whether that meant the lack of time limit or simply the Potara also providing a bigger power boost.
Granted that the lack of time limit is mentioned separately, which people use to conclude as a way to attribute Kaioshin's line as denoting a bigger power boost, but the Potara's amazing power was also mentioned separately by Elder Kaioshin when this latter stated he thinks not even Super Saiyajin would be necessary for Gokhan's succeeding against Boo:
Chapter: 502 (DBZ 308), P1.3
Context: Goku asks if he should become a Super Saiyan before merging with the Potara, and Elder Kaioshin advices against it
Elder Kaioshin: “If you’re going to become a Super Saiyan, it’s better to do it after merging. But anyway, even without doing that, you’ll probably be plee~~eenty. The Potara’s power is just that amazing!”
So, wouldn't that count as the Potara's power being also mentioned separately and therefore invalidating the "greater effects has to mean power since the other two advanatges were mentioned separately" argument?