I tried both of these watches on a few months ago. If I'm not mistaken, the advantage of the Overseas is that it does have a seconds hand and the RO version of the Dual Time does not, and greater water resistance. Most people will also agree the bracelet of the Overseas has more flexibility in feel and may make the watch feel more comfortable when on the wrist. Still, even with these advantages I still prefer the RO version. I just like its design, but thats purely subjective. Its a watch that is on my "must have list."
Good Luck and let us know what you decide.
Best regards,
Dino