It depends on how close you are to each of them. 6PN can carry with any random team slap onto him in a lot of cases, while Minato Jonin+5KM also have their own advantages. Personally, I'd go for 6PN, since he can't be cc-ed at the end of a round and carry-over to the next like Minato.

Given said that, it would probably help to know what ninjas you've already gotten, so that I, and anyone else, could give better advice on whom to focus on first.