MO in paris is not really on my radar given my preference for hotels like George V and Plaza Athenee (I like most of the Paris grande dames and a couple of boutique hotels).

le Meurice and Plaza Athenee are both Dorchester collection hotels with many similarities, but in a different style. They also attract a different clientele to some extent. Le Meurice is a beautiful classic Parisian Palace with everything you would expect from Dorchester Collection in terms of comfort, service, F&B etc...

Plaza Athenee is a beautiful hotel that manages to put a more modern twist on a classic Palace. It is very popular with a certain clientele of whom many come for shopping given its location on Avenue Montaigne, and it also attracts a younger clientele than some of the other grande dames. It is very popular with Middle Eastern guests.

Some may find Plaza Athenee to be a bit more ostentatious (or maybe a lot more) than some of the more understatedly elegant hotels in town. Although normally I don't like that quality in hotels, staying at Plaza Athenee is a guilty pleasure of mine I suppose. It is a very well run hotel and has great F&B in the Alain Ducasse restaurant and Relais Plaza.