As said before it depends on the writer and it depends on the situation, but lets break it down.

If Tony Stark is not in the Iron Man suit, Batman would win in most incantations of the character Batman and the character Iron Man. (Though the nano machine iron man may stand a chance.)

Batman's abilities are his genius intelligence, strategic thinking, his detective abilities, olympic level strength/endurance, martial art skills, stealth, and assorted utility belt gadgets.

Stark's abilities are his genius level intelligence (arguably higher than Wayne's), iron man suit that vastly increases strength, vastly increases speed, grants flight, greatly enhanced durability, flight, repulsor beams, missiles, etc.

Iron Man (if he is suited up) is going to win any melee for he is stronger and faster than Batman, a single hit is a one hit ko.

Iron Man is going to win any middle to long range battle for his weapons are designed to for medium and long range attacks.

Stealth is not going to save Batman when Ironman has targeting computers and the ability to see in the infared.

As for utility gadgets Stark's suit is far more versatile than Batman's belt. Iron Man suit is capable of "magical" acts such as 3D holograms to act as decoys, force fields, creating sonic blasts.

So in sum, Ironman is going to win the vast majority of these conflicts.