Until I get my hands on one I can't say for sure, but the GH4 sensor is larger. Generally that should mean less noise at any ISO level. Obviously the GH4 shoots in 4K (on the ground that's great if you have an Atomos Shogun, for example, but it's less useful in the air with only 100Mbit/sec data rate). So, the real comparison that matters is the GH4's 200Mbit/sec 1080p vs. this new micro. The micro has a better recording format and data rate with a global shutter. The GH4 has the larger sensor and a very very good 1080p file.
For overall use, I would take the GH4, especially if I wanted a nice option for stills or 4K on the ground. For air use, the micro might just be a bit better (a maybe more than a bit better) as long as one is comfortable with great 1080p in a world where there is a lot of talk about 4K. The global shutter is the real wild card, but if that costs dynamic range then it may not be that great.
Can you link a source for the loss in dynamic range with the global shutter?
As usual, the megapixel wars can overshadow what really matters. In my view, 4K gets to be an interesting and really useful option when it has the quality of good 1080p at the pixel level, just in a file with 4x the pixels and data. That means a bitrate of somewhere in the 300 to 400Mbits/sec range or higher. Nobody offers that in a compact size right now, but they will. Just on paper, one option out there was just announced this week: the Canon XC10 with 305Mbits/sec in 4K. But, it's a fixed lens design with a 1" sensor and not really ideal for flying.
http://nofilmschool.com/2015/04/bla...mera-studio-camera-4k-price-cost-availability
Looks like an amazing camera that was tailor made for aerials. Unfortunately it seems like there's a lot of pressure to shoot 4k. Even if it's not very useful. Kind of a litmus test.