I've put my D700 in the 防潮箱 and grab the GM1 with 12-32 kit lens (full frame equivalent is 24-64mm) for travel. The size was just like a DC. But the IQ was much much better than those 1-inch high-end prosumers.
The reasons for getting the GM1 : sensor size (M4/3) and camera size. That's it. And I don't need 4K video, anyway.