Well his Kage version just recently got buffed. Gave an interrupt to his ability and can interrupt the entire lineup if you target the tagged unit. Most people dislike the Kage version because his lack of chase. Also he doesn't currently scale like jonin does. Jonin c*so use his mystery virtually every round if he combos where as Kage cant. In the future, probably very far...kage will receive even more buffs. He receives the same scaling buff as flak jacket(12% combo/9% attack), skillbook will grant 40% res buff for the entire fight, and his most recent buff, can interrupt up to 9 people on a field which is pretty ridiculous when you think about it. So he will become a monster in Ranked and GNW.

As far as choosing between masked man and jonin....it really depends on your playstyle. Minato will give you damage output over the course of the fight, but he has to SURVIVE. That cannot be stressed enough. If you have trouble protecting him, throw someone with super armor in front of him. Masked Man on the other hand, shuts down any blitz team. Also does well against healers. Fits into almost every team as well and high chase damage with immobile. Honestly, Having BOTH in your team makes you terrifying. Especially playing earth or wind.

Gameplay with all the buffs to his Kage (fast forward to 3:40 for the mystery)