Of course a PH generally beats a GH, but in your circumstance (spending most of your time at the hotel) I would probably choose the GH. The Grand Club is one reason, but also the restaurants and bars provide more variety at the Grand. The main benefit of the Park is the serenity -- the pool area is pretty, and many (or maybe all) of the rooms have nice balconies on which you can sit and enjoy the sunset over Dubai Creek.

These are really two very solid hotels. Locations are equivalent -- both fairly close to the airport and not far from one another.