The slightly better gas mileage? Though now with CVTs that are computer-controlled, they get better gas mileage than cars with standard/maunual transmissions.
Lower maintenance costs are usually mentioned as an advantage of manual over automatic, but slushboxes have been around for quite a while now. With routine maintenance and average use (meaning no launch control usage or burnouts), both types will last forever.
Fortunately the fun factor has gone up by the same amount so I don't care...