To summarise above and put my own 2 cents - there is no "correct" one. Deployant clasps at Omega are available at 16 & 18mm, both will work with any strap that has proper ending on the clasp side (not standard) and proper lug width at the case. Rest depends on what you prefer - small taper (then take 18mm) or bigger taper (than take 16mm), polished or fully brushed surface on deployant (that mostly depends on character of watch case).
For the new Moonwatch Sapphire I chose 16mm deployant (to reflect big taper on original bracelet) with polished surfaces and bought tailor made alligator strap, which is cheaper & better than Omega.