Sonny is correct-we've been on Mariner twice- mid ships would be the best area just in case you should get a little sea sick-we were in 9602, Port side, and barely felt the ship move. Also, towards the rear there are more elevators than at the front (four on each side, as compared to two in the bow). Other than that, who's really in that much of a hurry that a few less lifts would make that much of a difference.
Hope you have a great time!!