Poll
80%
10%
10%
in a straight up battle, luthor in his armor would demolish tony. however, giving them prep is what makes this tricky [for me, at least]. i'd probably lean towards tony more times than not, mainly because of his 'extremis/control over machinery' component. having said that, luthor certainly isn't a feeble minded slouch. if he could find a way to disable tony's armor [ala some type of alien virus] he could most certainly take this.
honestly, i'm just not sure - but if i had to pick a winner, i'd give tony the slightest of nods.