The GH4 sensor is larger, but also higher resolution. The difference in actual pixel size isn't that extreme, the GH4 is maybe 20% larger pixels. And yes, the GH4 records to cheaper media with much smaller files. But it's also an inferior codec to record to. The XC100 is 8bit 422 internal at 305mbps. GH4 is 420 100mbps. That's a MASSIVE dump in compression. $2500 for the XC10, or $1500 for the GH4 and another $1000 for a decent lens. Call it "oversimplifying" if you want, but it's the truth. At $2500, the GH4 has options for better lenses and a (marginally) larger sensor, but the XC10 has a substantially better codec. In regards to the FZ1000, it may have a leica named lens, it might even be leica designed, but at that price point not a snowballs chance in hell it's leica manufactured. The FZ1000 also has smaller pixels and yet again, another inferior codec. It might get "close" to the XC10 if you have a very loose definition of the word close.