Just my opinion as always, but I prefer the traditional 16600 as "The Sea Dweller", I know there were many before and will be many after but it just feels so right on the wrist.
I love my SD50, but I'm only keeping it with one eye on investment, something I could do the same with on a SD4K. If I could afford to keep both I would and I guarantee the 16600 would be worn much, much more than the new model.
As a diver, the old watch feels like it was designed to be used, the new ones as jewellery.