depends, i am using Shiba dog , but i want Katsuyu for example.. Pakkun can help you proc the dodgers and can be used with hokage minato as well, also if you play your main ninja in 1st position lets say water main with shark bomb and neurotoxin pakkun is great. All the summons are wonderful depends your situation and your gamestyle!

I'd say it depends more on the line up than a "main"

for example, Pakkun fully upgraded might be better for Death Hidan than say Han/Roshi/Sailor Sakura/Water Main.