Thank you for clarifying this.
So then what makes for an optimal DSLR video recording camera?
I know audio capabilities are off the table at this point.
Lens acceptance capabilities (largely circumvented with various third party adapters?), frame rates, and software?
What's the advantage of a wildly more expensive Sony NEX-FS100U or Canon 5D over a GH2 (plus separate audio) if 1080p is the ceiling?
Are there some people with a genuine need for a tiny DOF to make that big sensor worthwhile?
Otherwise, what's the point of even going hog wild with all the Red hoopla?
The NEX-FS100 is an actual video camera with all the video-centric features that DSLRs are missing, including audio capabilities. Its sensor is also exactly the size of Super35 film, so many people like the idea of it being closer to film standards. It also has better color depth than the DSLR cameras.
The 5D has a full frame sensor, which is much larger than Super35 film and other DSLR sensors. This allows for an even shallower depth of field than film, but in actual function there's not much use for that. The larger sensor makes it better in low light, but this is more dependant on lens than sensor. It's also one of the very first video DSLRs, so it's been around long enough to gain a following and be used on many big projects. Since it came first it got a lot of publicity. It suffers from moire and aliasing issues, but if you plan well you can shoot around that. My main concern is that it's been around since 2008; it needs to be updated to remain competitive with newer cameras such as the GH2.
The GH2 has a m4/3 sensor which is slightly smaller than Super35, but its sensor for video is actually larger than other m4/3 cameras. It deals with moire and aliasing far better than the Canon cameras, but that can still be an issue in certain circumstances. Due to the m4/3 mount and lack of internal mirror it can mount pretty much any lens in existence that will cover the sensor. This includes PL mount cinema lenses and Canon FD lenses. The Canon is more limited in the lenses it can mount. The GH2 also resolves more detail than the Canon camera due to the method it reads data from the sensor.
The RED cameras have a sensor approximately the size of Super35 film (I think), its capable of higher cinema resolutions, better color depth, better dynamic range, and overall puts DSLRs to shame. Of course, all of that comes with a big price tag.
I'm at work right now so I did all this by memory and am typing this out on my phone. If anything's wrong I'll correct it when I get home.