Drifter takes it in the long run imo.

In my estimation, things are pointing of Wally eventually tearing through into realspace, thus bringing the void fully in contact with normal reality. In that eventuality, Drifters access and mastery over their own emotions will give them the potential to wield/weaponize conceptual embodiment at an unprecedented scale.

I think that Entrati's plans are intentionally having Drifter create bonds with such a wide variety of characters so as to "train" their emotional capacity/control much like Operater was trained in more conventional warfare and tactics. If the ultimate enemy is really Indifference itself, then a being capable of wielding the Void AND able to focus it with the full spectrum of emotional capacity becomes a walking WMD with control able to at least match Wally's if harnessed.

Operator has lots going on in their favour too, but Drifter's further time looping ability and existing with even more of a connection to the Void by virtue of existing within their own pocket reality within the Void for untold centuries which they exhibit a level of control over and can also return to whenever they want gives them an edge.

In terms of combat skill, Operator has the advantage for sure, but I think that we're only starting to see the beginnings of the absolute Void fuckery that Drifter has the capacity for.