I've stayed at both the Westin (though it was the I.C. in those days) and at LeMeridien Etoile (just a few months ago).
LeMeridien is not of the same caliber as the Westin, I would say it's more like a nice HolidayInn, and has a very 1980's-glamor feel to it. It's very clean, and the staff is very professional.
If you'll be traveling a lot by Metro, then you're in luck because Porte Maillot stop is virtually just across the street.
It is deceptive, however, of this hotel to call itself Etoile because it's not all that near Etoile/Charles-de-Gaulle. Though it is on the same Metro line.
We had 4 rooms for 8 people. Each room had 2 bathrooms (one well-sized and marble-appointed, the other barely big enough for a toilet). I think the hotel is delta-shaped, so you either have rooms facing the inner courtyard (and thus other rooms) or you can face out. The inner-facing rooms' views are rather boring, though quieter than their counterparts.
I hope you enjoy your stay!!!