I agree with JeffreyWalther.
not trying to be snarky, but if I had that kind of money to buy those kinds of cameras, I wouldn't be asking here.
don't care, too busy filming stuff
I have two eos-m cameras, the first I bought new as a refurb from Canon for $250 discounted from $700 and the second used for $150 that with the free Magic Lantern software that adds many cinematic features could last you a lifetime, all the camera you will ever need. The downside is bragging rights with filmakers that are snooty about gear. These people real interest is in acquiring gear and bragging about, but have much less interest in actual filmmaking. The point being you can make terrific looking movies with the Canon eos-m that will look great along side cameras costing tens of thousands of dollars with how people view films in the real world (streaming, blu ray, youtube etc)
I think the GH4 can be a good choice, but do not think it blows all others out of the water. I also think my $150 Eos-m is a great choice and I doubt that anyone can tell the difference in quality in how video is viewed in the real world. The camera body is just one aspect and any of the popular cameras and many dslr made in the last 5 yrs will work great for you. The key just like in guitar playing is how much skill do you have? If you think that the camera body will allow you to take great video, mostly what you will have is bragging rights. If you learn how to use any of the well known dslr and mirrorless cameras for video and learn to set them up, compose shots, light well take your pick, they all will look about the same from a used $150 eos-m to a Red costing tens of thousands. All will be effective movie makers. Just like you can buy a used car cheap or an expensive Mercedes for transportation, the low cost kia will get you there just as fast. Camera bodies are like that. People will argue about rolling shutter, the easy solution, don't pan so fast that you get rolling shutter or noise in ISO settings, light your scene well and you don't have to worry about Iso. The fact are if your skills suck they suck with an expensive or inexpensive camera and the same is true if you acquire great skills. My recommendation is to look at your budget for camera, lens, audio and lights. You will find that a modest priced used camera with good sound and lighting, used skillfully will trump buying an expensive camera body with a crappy lens. https://www.youtube.com/watch?v=Gb58PSxuj8s
I have to agree with the other two posts, the free magic lantern software gives you a bunch of video controls that you will want to have. I have Canon T2i, T3i and two Eos-M. I bought one eos-m from Canon refurbished at $230 and the other used for $150. Magic Lantern is free and there are a bunch of youtube videos on how to install and use Magic Lantern which is only for Canon cameras. I think also you will find when these cameras are used well, no one in the audience will know that you made it on a $150 used Canon or a $50k used Red. There is more to great video than the camera body, but it really is good and as you go up in price you aren't going up in quality very much that an audience will notice when the camera is used well.