The JW Marriott is very secure but I did find the decor dated and the rooms a bit tired. Their airport pickup service is amazing though, you get treated like royalty. I have reviewed this hotel in my Mumbai trip report.

I don't know of the other hotel, but I stayed at the Grand Hyatt which was fantastic.

Just a warning, travelling around Mumbai can be a nightmare, with long car journeys stuck in traffic. Just bear that in mind when you are planning your day. Whichever hotel you stay at, ask them to arrange a taxi. AVOID the 'local' black and yellow cabs and stick with the 'coolcabs' (blue and white) or 'meru taxis' (green), they tend to be reputable and also have aircon!