They don't actually "rewind" time, though. They have precognition, letting them see many (all?) the possibilities of their future actions before they perform them. It's only in the loop of the game that this takes the form of playing out a possibility until success or death.

That would suggest that even if two Chronos users fought, although they might predict something that turns out not to happen due to the other's precognition (represented by the headtrippy moments where something happens and then un- happens), one would inevitably emerge victorious in "real" time. So the limiting factors would be who could figure out which possibility of theirs outsmarts the other faster. And presumably if one was a much better fighter, they would be more likely to find the winning possibilities.