The new 18-35mm
The MFT curves are similar to the ones in the 16-35 f/4 at the wide end, the latter is better in the longer end.
This could be a handy lens for carrying along with the D600, much lighter than the f/4 zoom, 385g to 680g, and also much smaller, 83x95mm compared to 83x125mm (more than an inch shorter). Likely a better balance on the D600 as well.
It lacks nanocoating, if I read it well, so resistance to flare may be worse. It'll be inetersting to see the distortion characteristics of the lens. It's about FL equivalent to the 12-24mm that I have used extensively on DX bodies.