The 5711 offers the "umph!" of the unmistakable and iconic Nautilus design (albeit at a premium). However, if you are not a fan of the Genta design or care little about the hype, the 5711 is "just" a simple, waterproof "luxury sports" watch with a see-through case back.
On the other hand, the 5146, as you mentioned, offers great value and represents much technical prowess with its annual calendar and moonphase display functions (at a reasonable price). However, if you don't really need to be reminded of the date (up to the month) or the phases of the moon, then getting the 5711 (plus maybe another simple watch) might be a more practical choice.
Of course, these are just my personal opinions. In the end, both watches represent the best of two, different worlds, and choosing one will eventually boil down to what you desire or value in a watch. Good luck!