At this point, most powerful DBZ characters are Godku, Beers and Whis, with Beers being a casual Solar System destroyer, and thus multi SS level at his 100%.
We also know that, for comparison sake, Godku is 6, Beers is 10 and Whis is 15.
No one of them can keep up with Prime, as far as I'm concerned, but a Ssj God Vegetto I think could, and quite well at that: in fact, we know that Godku power is the result of combination of the Ssj God boost and base Goku's level.
Now, given the huge gap base Vegetto had over base Goku (base Vegetto >= Ultimate Gohan > Ssj3 Gotenks >= Super Boo > Ssj2 Gotenks > Ssj Gotenks (post RoSat) > base Gotenks (post RoSat) > Ssj3 Goku > Ssj2 Goku > Ssj Goku > base Goku), a hypothetical God Vegetto would come up with a level in the high thousands (if not millions), compared to Whis being at 15, for example.
So yeah, Prime could even get his ass kicked by that Vegetto (but Guardian Amped Prime would still win).
The part of the show in which base Vegito battled Buuhan for a while is non-canon anime filler. In the manga, Vegito transformed into a SSJ almost immediately after conception--he never battled Buuhan for any length of time in his base form.
Though in this particular forum, the anime may take precedence. Dunno. /shrug
That's just opinion. The exact line from Whis(in the official English dub) is as follows: "Attention! Please watch your language, lest you offend Beerus. Otherwise he won't just destroy the Earth, but the entire solar system as well."
The ease in which Beerus can solar system-bust was left ambiguous, at best.
When there's a contradiction between manga and anime, manga obviously takes precedence; in this case however, base Vegetto makes his move only in the anime, so him being that powerful contradicts nothing.
Anyway, even if you don't have him around Ultimate Gohan's power, base Vegetto must still be worlds ahead of base Goku, since as a mere Ssj, embarassed Boohan, the strongest DBZ villain, without using his arms; also, Ssj Vegetto is so far above Boo that he was the only one (alongside the Genkidama) able to vanish Boo up to molecular level.
That's not an opinion.
Also, you shouldn't go by unreliable dubs, but only by original japanese lines.
Indeed, according to Herms' translations at Kanzenshuu, the original line from Whis says: "「あっという間に太陽系ごと破壊されてしまわれます」", which means, literally, that "“The entire solar system will be destroyed in an instant.”
Now, besides the fact that this line must make Beerss massively FTL in speed and/or energy spread, we also know, from canon manga and official guidebooks as Daiz and SEG, that SPC "has enough energy to destroy a SS".
All of ths easily makes of Beerus a Multi SS level threat, unless someone wants to deny official canon sources, in which case I have nothing more to say.
Also, finally, going by english dub they make Beerus even stronger, since he is portrayed as a Galaxy cluster destroyer (line which doesn't exist in the original japanese translation).
I'm not saying Beerus can't wipe out the solar system in one fell swoop, btw. Just pointing out the English dub's line is all.
No need for these long and unneeded write-ups. I'm just telling you that the scene you're using to judge Vegito's base PL is non-canon anime filler. That is all.
Not saying he's wrong, but telling me that I should hold a fan's translation in higher esteem than the official English dub is kind of silly/ironic.
I'm just telling you that original japanese work is > any english dub, which is just a subordinate source in quality.
You don't have to tell me base Vegetto's fight is filler, I know that.
That's why I wrote that long write-up, as you called it.
Fan translation?
Err, Kanzenshuu is the most trustable DB surce you can find worldwide on the internet, and amongst them, Herms is probably the landmark.
When it comes to DB, this is the best source bar none, and DB enthusiasts know that.
English dub is just rubbish in comparison, or, to better say it, it's decent when you want to have fun watching the show with your friends, but it isn't even worthy to be considered when debating or when you want to really know even the smallest detail about AT's work.
But this not because it is the english dub mind you, it's the same with everything that isn't the original japanese source.