We know Hourman can summon up past versions of selves, and that he can put someone in stasis outside of time (Which is how he protected the JSA from Extants time altering effects)
So couldn't he use those powers on himself to make the hour of power time limit irrelevant?
Didn't Ares display some kind of time stepping ability against X-Man due to the nature of war itself and it existing at all time or something similar?
I also think Hourman's offensive time manipulation such as time vision would fall short simply because Extant tried something similar to Hippolyta who was immune due to her status as an immortal. I'd imagine Ares enjoys benefits similar, if not greater, due to his status as an actual god, not an incredibly long lived mystically enhanced human.
That being said, I do think Hourman probably wins more often than not.
Extant could have devolved her instead. He straight up wiped out Kent Nelson and defeated Metron, with his standard powers..
And if Hourman with only his "Hour of Power" can mess up Amazo with half the Warlogog or Extant with the 99% full Warlogog, I can't see Ares having much protection from it.. He's not an abstract, and still has points of history Matt can tap into, and even if he didn't Matt has a lot of other tricks up his sleeve, like simply banishing him outside the timestream..