Most neophytes to Rolex see the Sub and the Sub Date and just assume that one has a date, the other doesn't, and that's the difference..
Of course, this is not true. They are completely different watches..
Here is a bit of trivia to amaze your friends:
.........................
Sub.................
Sub Date
Case Size ........ 39.5mm................ 39.5mm
Case inc Crown . 43.50mm..............43.60mm (difference could be possible to a higher seated tube)
Bezel Diameter... 39.5mm ...............40.00mm
Thickness.......... 12.20mm ..............12.55mm (Sub Date middle case is thicker as is the bezel)
Crystal Diameter..29mm ...................30mm
Visible Dial..........25.5mm..................26.5mm
Lugs.................Holes..................No Holes (since ~2001)
Weight ............ 127 grams .............. 135 grams
Hand length.....................same.......
Almost nothing on these watches interchanges except the hands and Triplock Crown... Even the bezel inserts are different to fit the different size bezels, and they use different (although interchangeable until SEL's) bracelets.... Since they do use the same hands, it gives an illusion that they are longer because of the smaller dial..they extend into the markers more..
Attachment 136354
Here you can clearly see that the Bezel on the 16610 is thicker than the 14060 by comparing the undercut beneath the bezel grip surface:
Attachment 136353
Another difference is the machined ledge on the backside of the 16610 (right) for the fitment of an SEL bracelet. The 14060 does not have suich a lip or ledge and an SEL bracelet cannot be fitted to this model without modification..
Attachment 136355
Since these watches are made independently, and since they have continued on with the legacy of the original (nostalgic) Sub in the 14060M; I believe it will continue in production..