Just got the 15400ST Blue Dial yesterday after I let go two of my pieces. Will do a detailed review later. In the meantime, I will do a brief comparison between the 15400ST Royal Oak and the Royal Oak Offshore.
Side-by-side comparisonDespite the Offshore being merely 1mm bigger than the Royal Oak, it looks more imposing. On the wrist, as far as the eye can tell, it looks bigger as well. The Offshore always feels like a 45mm when it is on the wrist. In comparison, the Royal Oak wears more like the Ceramic models from Rolex.
Thickness comparisonThe Royal Oak Offshore is comparatively thicker as compared to the Royal Oak. I cannot accurately describe the difference in weight between the both as they are made from different materials but arguably, the Forged Carbon Diver feels lighter on the wrist as compared to the Steel Royal Oak. As for the wearability, the thickness of the Forged Carbon Diver means that it is more suited for casual wear. I tried countless times to slip it under the sleeves of my shirts but the fit is very tight. I do not think the Royal Oak would face this problem.
CasebackROOMy ROO Diver is the older variant and I believe the newer ones come with the open caseback.
http://i759.photobucket.com/albums/xx236/gmac88/Mobile%20Uploads/image2_zps47e4a4b2.jpg[/img]ROThe RO has an open caseback for me to admire the 3120 Caliber beating inside. Incidentally, this is the same movement in my ROO as well.
Thank you all for viewing.