It is better to a superior room in a more moderate hotel or a standard room in an expensive hotel?

It depends...if you would require the use of an experienced concierge or a larger restaurant, perhaps the smaller room in the grander hotel. Otherwise, I'd go for the grander room in the smaller hotel.

RichardJ, one more thing to keep in mind in Paris. While the "superior" rooms may have nicer fabrics or furniture, it is more likely that it has MORE ROOM and/or a better view than a standard room. You know how tiny those rooms can be...