Great fight idea.
Both characters are pretty ruthless.
The question's going to hinge on whether people think Luthor's armor can withstand Mandarin's IM armor damaging blows, and how the ten rings are viewed power wise.
In my case, i think Luthor would take a drawn out "comics" battle, which'd be fun to read. In a standard no prep forum fight, which this seems to be, i see Mandarin having the power and skill to get the win.
Lex with battle suit has very impressive showings against Supes and company.
Still, i have to say his armor isnt as powerful as IM's, which Mandarin has damaged using chi and HTH.
Add the rings, which are a more varied power set than Supes brings to bear, and a ruthlessness to match his own, and i really believe Mandarin takes this.
Just expanding on my previous post. Slow on the board tonight.
Given IM's popularity since the solo and Avengers movies, i'm surprised Mandarin hasnt become a bigger player in the MU.
Is he still considered Tony's arch enemy?
IIRC Lex's suit was specifical designed to fight Superman though ei Kryptonite. I think Lex is probably a great deal more intelligent but he isn't very accustom to direct combat.