Depends on what you're looking for. Westin Vendome is better located for all the tourist sites and in a busy high rent district.

Renaissance Trocadero is OK, nothing to write home about. I stayed there to be close to my daughter this spring. Breakfast buffet is reasonable. I checked out the room (what a MR Plat can expect as upgrade) at Renaissance Arc de Triomphe earlier this year. Location is a little out of the way from Arc de Triomphe. The room is fine, hotel is fine but not very interesting. Westin Vendome is in an old building with a lot of character. Neither Renaissance has Lounge.

Personally, I would select Westin Vendome (or W Opera, now that it's lower category than years ago) over any of the Marriott properties.