Paris hotel using Bonvoy or Hyatt points

There are some very nice Hyatt properties. Hôtel du Louvre comes to mind as historic but expensive. If you have the points, go for it.

I have done the Marriott Rive Gauche. It was nice enough. Not exactly a french experience but it was nice.

I can say that the Hotel du Louvre is newly reopened a few months ago after a complete remodel. Its location is very central and quintessentially Parisian.

Personally, I prefer the Marriott Ambassador on blvd Haussemann to other Marriotts. The Left Bank hotel in the 14th is rather away from anything other than the catacombs and the location on the Champs Elysées is probably too noisy with too many tourists.

I believe the Westin Vendôme is also a Bonvoy hotel and would also be worthy of consideration.

Indeed it is.

There are a lot of Marriott and Hyatt properties in Paris. I suggest staying in one of the lower numbered arrondissements for ease of access to the main tourist sites.
On the Hyatt side, in addition to the places mentioned, there is the Hyatt Madeleine, which is a very nice property (stayed in the summer of 2013). It is not as central as the Hotel du Louvre but it is lovely. If you have the points, I recommend considering the Le Pavillon de la Reine, Relais Christine, and Grand Hotel du Palais Royal or really any of the hotels in the SLH program that participate with Hyatt points. I've been to the three that I mentioned and they are three of my favorite hotels in Paris and all are very well located.
On the Marriott side of the equation, in addition to the places mentioned you may want to consider the Renaissance Paris Vendome Hotel. It often has availability for points when the Westin does not. I like the location and room size better than the Westin but that is because I do not like exiting the hotel on to a very busy street and you come out of the Westin right on to Rue de Rivoli. Another thought is Le Roch Hotel & Spa. Sadly, I have never stayed there -- I kept eying it but it had no availability and now I no longer stay in hotels in Paris.

We are set to stay atHotel du Louvre April 16 to 22nd, so hopefully i can report back (we didn't book on points as this is for work so the company paid). Hopefully the conference and/or flights dont get canceled.