If you have the $$, go with the Really Right Stuff BH-55. I have in the past owned Acratech and Manfrotto ball heads. They work fin but if you have a heave lens plus your camera, the ball head will creep on you. Also you do not want a Aluminum Tripod, they are heavy and cold to the touch, and worse in the winter.
When I received my Acratech GP I mounted my Nikon D3 and the 80-400 lens - the two of them do weigh a bit. No matter where I moved them the head did not slip one iota.