Batman might have lower polygon models, worse textures and technically inferior lighting, but it has so much better art style and art direction it looks waaaay better as a whole IMO.
Yeah, texture fidelity is one metric but for textures really how good or bad they are depend much more on the skill and attention to detail behind making it more so than raw numbers. The models themselves is really the only part where the increased polycount actually shines through and makes it competitive because it is so important to make things like hands, hair and clothing look "right'. But the aesthetics of SS is just so bland and flat that it ends up looking like an old tech demo.
I think they went for more comics book instead of noire vibe. But it did not went well. It looks really bland, flat, washed out, call it howewer you like. It surely has some potentialnin it, but overall it just doesn't click. Maybe low contrast among other things?