I don’t care to find the source right now, but around the time when the OLED came out, the battery performance was nominally better in third-party tests. It did come down to specifics in what you played (game optimization) and how you set the power profiles, but the extra battery didn’t add much in terms of playtime—maybe an hour extra in real world use cases.

I don’t know if that’s still the case; it could be that Valve has OLED specific improvements by this point, but I suspect that it still would not be a significant enough point for someone to decide upon a model just on battery specs.