I have the GH3, and had the FS100. I'm not sure rigging a GH3 will equal the price of c100, unless you like spending money.

There could, and would be different reasons to have either of the three for specific shoots.

Fs100's are around 3000 to 3200 used, but for documentary, and run n gun you will have to be constantly aware to prevent the sensor reflection that can creep up on you, but other than that it gets the job done beautifully.

You will need all that crap with the C100 too! You need lenses, rails, FF, all the same stuff so it won't even be close and you'll have to deal with all the problems the C100 presents. You're pretty much looking for a camera that can do the job of multiple cameras. IMO you better go with a fixed lens camera. I know people will jump in and say this camera is fine for this and that camera is fine for this too but you something durable that presents the least likely chance of getting ruined by dust, dirt and water. I've seen beautiful stuff shot on the Sony EX3 and EX1. Maybe an updated version of something like that or even a used one.

@vicharris will you know that the C100 it comes with lens and it has ND on as will, what about GH3? and output to black magic shutter 2 recorder which I think gives you 4:2:2 and high bit rate as will.

Thanks

A C100 body is $6000 alone! Now you talk about throwing a BM recorder on it. You are making a large camera package there with shit hanging all off it. Not good for Documentary work. If you want an all in one camera you should look for a fixed lens, built in ND, XLR and in camera 4:2:2 50mbs recording rate+. It's just my opinion and I am by no means an expert but I think all those Cinema cameras Canon is putting out are way overpriced boat anchors. It just depends on where you stronger area will be. I don't have any experience with the GH3 but you can't compare price in those first three camera. A finished shooting package price of the three are very different. You still need all the crap for any of them. They aren't shoulder mount cameras. You need to figure out what you want to spend and go from there, not just throw camera names in the air and see what hits the ground first.

@bashir

I really suggest set of two cameras.

One - GH3 plus JuicedLink preamp for audio (with XLR and phantom power).
Second - Panasonic X900 (now on sale and cheap) or if you'll have some left - AG-AC90 (it is almost same camera internally as X900)

Add here small and light rig.

So, you'll have two cameras for interviews.

Suitable small sensor camera with very good range and stabilization for fast docs.
And in same time in GH3 you could have both small DOF guys so like, and ETC mode that you could pair with X900 if you need small sensor appearence.

As for NDs. Get small 4x4 holder + Glass ND set + 82mm converter + 82 variable ND (where you need to change fast). It'll work on both cameras.