Okay here's what I think:
The Third Eye are more versatile, and have more abilities that put them in a big advantage. IMHO Vetto is more of a meat shield than anything. Fana and Raia will be hard carrying their team. If I were to imagine their formation;
Vetto will be the main fighter, going crazy and brawling. Also tanking most attacks due to his crazy endurance, once he transforms, his regeneration is incredibly broken as well. BUT he isn't just a crazy brawler. He has Ki which will make fighting him incredibly hard as well. He was also able to find several weaknesses in Asta and Kiato's fighting style (though the Sannin should be more skilled than Asta at that point).
Fana heal and AoE Spam. She can pretty much heal all damage with her robes, and as long as she's in the battlefield, I don't believe the Sannin have a chance in winning. Their best bet imo is to defeat her first. She can also spam her massive fireballs which they'll have no chance in avoiding unless they use Shunshin (although not in character for them to use, I don't see why they wouldn't use it against fireballs that they have NO chance in dodging otherwise) (Oro can also use his Rashomon Gates to block them).
Raia is the brains and support. With his massive versatility he'll help his team keep the Sannin on their toes with his hard to predict magic, since he has so many.
It's been a long while since I've seen these three fight, so my knowledge is not nearly as extensive as it is with the Sannin, so many someone more knowledgeable can correct or expend on how they fight in character, their weaknesses, strengths, most useful abilities etc.
The Sannin are definitely overall smarter and IMO have way better team synergy and team tactics. They're less versatile, but make up with it due to their teamwork;
Jiraiya is fairly versatile; I think his best bet is to BFR Vetto and himself into a Toad's Mouth, where they'll fight inside. Inside said Toad, the footing is very unstable due to the squishy nature of the stomach, and overtime, if the opponent isn't able to escape, the stomach will digest whatever is inside. It's also able to secret odorless stomach acid/poison which makes it near impossible to detect. Within 10 minutes, it's able to fully paralyze whatever is inside. Itachi had to use Amaterasu to burn through so that he and Kisame could escape, which in itself is a feat, since the toad's mouth is fire resistant, since it uses fire breaths. Knowing this, Jiraiya would ask for his teammates assistance to protect the stomach from the outside, from Fana's fireballs, as well as summon his own frogs to protect it as well. (Oro's Rashomon would help greatly here)
Once in the Toad, he can use his Hair Jutsu, which acts like a shield, when used he can wrap his hair around himself to avoid damage. He can also just restrain Vetto with his hair, as he has the higher LS. Or use Earth Jutsu to create a swamp that'll trap Vetto inside.
Jiraiya can also use Sage Jutsu to help amplify his abilities.
Tsunade is probably the "weakest" link simply because she doesn't have much versatility. Assuming the plan works where Jiraiya separates Vetto from Fana and Raia, Tsunade has no way of hurting either of them due to their range and flight. Assuming this is in New York due to SBA, she can use buildings to get closer to them, but they can and will just maintain range, so she can't really help there. Her healing is also really good, especially with Byakugō. So she won't be put down anytime soon. With Katsuyu as well, she can help Jiraiya survive his deathmatch with Vetto in the corrosive toad mouth. She's largely a close range fighter, so she won't be able to do much unless her and Orochimaru manage to bring the two down.
Orochimaru is, much like Jiraiya, very versatile; Although my biggest issue with this key with Orochimaru in particular, is being unable to figure out how he fights in character, since he's never actually fought in this key TMK. However, by comparing what he has shown in earlier parts of the series, he's no slouch.
In terms of endurance and regeneration, he's able to instantly regenerate without issue and even shrug off Totsuka Blade and Tsunade's own punches. He can also stretch his body and elongate himself for more range as well as form a completely new body if his old one is damaged.
He can also go in surfaces to avoid damage and also approach opponents stealthily. He can also summon giant snakes to fight alongside him and also can control his sword using telekinesis.
Ngl I dont feel like going through all of his abilities cause it's alot..
Essentially he's dumb broken in terms of regeneration, ways to avoid damage via going through surfaces, substitution, making a new body, snakes etc etc etc. Orochimaru much like Tsunade will be INCREDIBLY hard to put down. He also has Rashomon which can protect from massive damage and big techniques that they might struggle to avoid.
I wrote alot, IK, I just felt like writing alot lol... LMK if there's anything that needs to be clarified, I'll be busy today and tmr but I'll try to get to responses when I can.
I'm neutral rn, not really voting towards anybody, although I am currently leaning towards the Sannin just based on my spiel here