SALMANPK
14003
The Nautilus wouldn't even exist if it were not for the Royal Oak...
It gave Patek the courage to launch the Nautilus, it is a known fact the original Royal Oak from 1972 paved the way for highly finished luxury sports watches, for that reason alone you should have the original, the grand daddy, the legend, a Royal Oak 
S
PS: I have to disagree with you, the Royal Oak 15202 is more refined than the Nautilus, the finishing and aesthetics of the case are at a higher level, the Nautilus is a nice watch and comfortable but almost flimsy compared to the Royal Oak 15202