How would we know ? Maybe there are some untested ones that are better, but we don't know because they haven't been tested. Did Iraq have "proper" Soviet hardware or some licenced and downgraded versions ? Iirc the USA and USSR usually exported inferior variants of their weapons to other countries during the Cold War to prevent reverse engineering. I think East Germany was the only country with a "real" Soviet arsenal because that would have been the frontline in an East/West war. Speaking of untested, exports and Germany: I think (maybe due to misguided patriotism) that the Leopard 2 is still at the top. It has the same (German manufactured) main gun as the Abrams, better range due to less fuel consumption, and superior protection. There were some articles last year that a few were destroyed in Syria, but those were old Cold War era models sold to the Turkish Army. The ones Germany still has (all five of them) have upgraded armor to operate in urban environments.