First thing,
Hiruzen knows all jutsus is false.you can say: he knows many jutsus or he knows maximum number of jutsus, but saying that he knows all jutsus including rasengan & ftg is just wrong.He might know the strengths & weaknesses of ftg & rasengan,but he doesn't know how to perform them (even tsunade said that only minato & jiraiya know rasengan)
Also,we havent seen hiruzen fight except against oruchimaru,which didn't show his(hiruzen) true potential.
About Minato,
he was easily stronger than old hiruzen, as many times this was said : I wish the 4th was here... (but as we don't know hiruzen (prime)'s potential, we can't determine the winner.
Also, during fight with Tobi, Minato was in total control & could've won if fight had extended...the way in which placed his mark on tobi & broke tobi's control of kyubi through contract seal (without even tobi knowing it) tells us how clever minato was.
About his encounter with A & KillerBee, he wanted to have a stalemate, otherwise he'd have easily killed killerBee on the spot.
Conclusion: Going by hype, prime Hiruzen is stronger, but going by feats, Minato is stronger as Minato's tobi/9 tails feat & encounter with A/B feat were much better than Hiruzen's oruchimaru feat.