The most notable change between the two models is the material used for the bezel. The ref 16610 makes use of an Aluminum bezel, just like older Submariner models; meanwhile, the ref 116610 introduced the Cerachrom bezel.
The Aluminum bezel has a softer, matte and more toolish look that vintage Rolex fans like, but the disadvantage is that it can still be scratched or dented.
The Cerachrom ceramic bezel was unprecedented, because it is impervious to scratching and fading brought about by UV rays and chemicals. Fashioned from extremely hard ceramic material, it keeps the watch looking like new for longer.