Last April we were scheduled for a Reward stay at the Hilton La Defense, which was the only one available in Paris. We decided to stay in the UK (London was our base) and stayed at the Hilton Cardiff instead. I think it was a good decision! The lounge had a magnificent view of the Castle and the lady in charge (Wendy) took very good care of us, including getting us a late check-out on the last day.
Sorry you had such a bad stay. I had to laugh at your observation that the lobby was impressive. Aren't they all? It's the room that's the real test of a hotel!