Grand Case has some of the best restaurants on the island. GC is also home to 2 Lolo's which are essentially bbq joints that you can get a great & cheap meal at! (I prefer the one on the left when facing the beach).
Le Petit is on the beach but doesn't offer a pool. Le Esplanade is a short walk to the beach and has a small pool. They are both very romantic. I've stayed at Le Petit (see my review) and it was wonderful. They are both more of a boutique hotel (i.e) we were on the 4th floor and had to carry our luggage upstairs.
Grand Case beach is beautiful however the backdrop isn't the greatest. Along the beach you have many homes / run down hotels and restaurants directly on the beach. There is one main road that runs thru GC and it has shops but mostly restaurants.
Are you planning on driving around the island? SXM is really the place to rent a car and explore the beaches. La Samana is a very popular hotel for honeymooners too!!! Have you checked that one out? We are heading back in 17 days (my 6th trip) & staying at The Westin. I've stayed at a number of hotels but I like the amenities the Westin offers. It is a bit out of the way but we have a car and don't mind driving.
How long are you going for? I think you should split the time between the two sides. Orient Beach is fun and gorgeous too! It's lined with little restaurants / beach bars.
I know how important the honeymoon is ~ we were just in Hawaii for ours last Sept :) Congrats!