> Katsuyu on it's own isn't that strong, but in combination with a Byakugo user like Tsunade/Sakura, it can be a formidable summon in team battles
It's best particularity though is it's defensive ability, because it's hard to kill without necessary amount of salt(if what Suigetsu said is correct)
> In terms of battle however, i'd say the toads are the most versatile. Gamabunta was shown able to hold his own against a non-fully awakened Shukaku in straight up combat, could counter his fuuton attacks partially with his own suiton attacks.
I'd say though that individually, Manda was portrayed just as strong if not stronger than Gamabunta in the sannin battle, however it's the snake most powerful summon with no one comparable outside of Orochimaru's yamata no orochi(and later on version 2 Manda created by Kabuto) when there are many toads capable to rival Gamabunta in might
Version 2 Manda graping strength was also amazing when Kabuto summoned him, so in terms of straight up power, Manda 2(if he is counted since it was a last minute addition created by Kabuto) is probably the most powerful summon
However overall i'd bank more on the toads, who are more versatile, not only they can do incredible leaps, they are well-verse in martial arts, ninjutsu and even sennin mode techniques, with Pa/Ma capable to immobilize people with sound techniques or/and defeat them with powerful genjutsu
Overall then, due to their number, quality, strength and versatility, i'd probably pick the toad summons