Who would win?

Both are geniuses.

Both are billionaires.

Both have access to high tech weaponry.

I believe that Ironman will win since his suit is designed for war while Batman were he to design a similar suit like Batman Beyond suit, its design to incapacitate the criminals, not to kill.

Batman

and it wouldnt be close.

Batman has powered suits too.

Batman most definitly you madman.
Batman would shatter iron man on all fronts.
If he can put up a formidable fight against superman then iron man should be no problem,