I like Mercure, but I like Ibis, so I think my standards are different from yours. But it's very true that the quality varies dramatically from one property to another, rather like Holiday Inn.

But if your event is close to the Metro stop, I don't know why you feel you need to overnight there. You still have to leave the hotel and go get in line at the venue. It's not as though you can go back and forth to your room. The only reason for staying there would be if the concert lasted until after the Metro stops running.

I'd just stay where I wanted, and take the Metro to the concert and get in line.

(Don't do the Crowne Plaza Republique. I've considered staying there in the past, but my research suggested it wasn't a good idea.)