As you know the new Overseas model will perhaps be unveiled in 2016, maybe it is worth waiting before choosing the Overseas.
I found the Harmony DT quite appealing when I tried it (here: www.watchprosite.com=).
However, I think that they are so different aesthetically that it is hard to give a good piece of advice without knowing what you're looking for.
The OS is much sportier, even if with leather strap (vs bracelet versions).
The Harmony has a very unusual case shape (compared to round ones) and an original dial layout (colors etc...).
It will be interesting to know which one you pick!
Cheers, Mark
This message has been edited by Mark in Paris on 2015-12-29 13:26:38