I've worked on two shows this year with the C300MKII, one a second unit cinematographer for a feature and one industrial show. Both shows I also cut and colored, which gave me some great opportunities to see what the net result was like. I personally love the color of the C300MKII out of the camera, it's just a good looking camera. It has all the bells and whistles. It's small, but it doesn't hand hold well stock. Like the RED's, you need a shoulder kit and do I dare say an "actual" viewfinder, as the screens the C300MKII come with, aren't good at all. The Canon also requires no setup what so ever. Battery can stay in it's little compartment and you can pull it out of the box, turn it on and start shooting after the 10 second boot time.
With all that said, the Canon C300MKII has TWO major flaws. The biggest one is processing power. Canon have gone cheap and use a 10 bit processor, which means the best it can record is a 10 bit 4:2:2 MPEG iFrame signal. This limits the over-all cameras potential, even with Clog capture. Is it bad? No... but it's not special in any way. The XAVC codec in 4k, is a nightmare to work with because it puts a bottleneck on any software, which means you've gotta transcode. This may sound like the normal way to work, but with cameras like the Ursa Mini 4.6k, Pro Res XQ native recording allows you to edit exactly what you shoot with a LOG color space applied.
I just shot a short film with a Dragon, which is very similar to the Raven and Scarlet, neither of which I've used on a show yet. I've shot with Epic MX and Dragon on several shows in the past but now I can compare my experiences back to back with the C300MKII.
I've never liked RED cine because they are an accessories driven company, specifically driven towards cinema. To make the camera work, requires a box of accessories that need to be assembled before you can run the camera. This is super annoying, especially for hand held work. You need a camera cart or a dedicated place to assemble/disassemble the rig. You need a diddy bag with you all the time to keep the tools in it for making small adjustments. The RED is designed specifically for decent sized crews, where there are cables running all over the place to different outputs and monitors for operator, AC and maybe wireless transmitter, all mounted on the body, THATS the "RED" market. It's not great for a single operator, trying to get simple shots and move on. The camera does not like to be hand held and it's very heavy for what it is.
Picture wise? The newest LUT's and software fix SOOOO many of the older problems. I'm actually happy using the Dragon today picture wise. With a decent graphics card, the Red media plays back perfectly fine in real time at high res. The amount of manipulation possible with RAW RED material blows the shit out of the C300MKII. So it doesn't really matter how beautiful the Canon imager is, you can make the RED imager look even better with a few tweaks. Plus, the newer imagers are 16 bit, which means even greater dynamic range. This year working with the newer software RED's have given me a new appreciation for the camera and I really enjoy working with it more then I had in the past with older software.
If I was doing ENG style shooting, if I needed a mic input and built-in HDSDI outputs for other monitors stock, if I needed a simple setup and take down, if I didn't need the best quality, just wanted something that works, I'd contemplate a F5 over a C300MKII. I personally would NEVER own a C300MKII... ever.
If I was shooting cinema style products, if my camera was pretending to be a film camera with no audio and one video output, if I didn't mind the setup time and was ok with the typical idiosyncrasies RED cameras have, I'd contemplate an Ursa Mini 4.6k over a Scarlet, for dozens of reasons. One of which is the simple fact you get the best of BOTH worlds. Small hand-held package with a decent screen built-in, easy to operate, but still very much a "cinema" camera. Yet, you get 14 bit RAW, you get 12 bit Pro Res XQ, you get 120FPS @ 2k (which is good enough) and most importantly, the color science of the Canon camera, without dealing with the horrible codec.
I like the RED output, I like the RED workflow, I even don't mind the menu's and touch screen interface. But they charge A LOT OF MONEY for something that's constantly evolving, where accessories for the new cameras, don't fit the old one's. Where they have proprietary and very expensive storage you MUST buy from them. Where break-out boxes to get audio and I/O are again, made only by them. So they can charge you $8k for the brain, but it costs $12k to build a working package. You can get an URSA 4.6k package out the door for $8500 bux, with batteries, shoulder kit, viewfinder and storage! No, it's not the best camera made, yes it does need an OLPF (which I hear is coming from aftermarket companies soon). But... it's by far, the best deal of the planet for cameras that shoot over 4k AND have a decent codec list for "cinema" shooting. Again, if you're going to shoot ENG, hands down, Sony F5. Used it, works great, doesn't look as good as the Canon, but with a few option boards, can shoot Pro Res and RAW, with high frame rate and SUPER AMAZING high ISO with very little noise. It's great for run and gun stuff, if you find one used, new they're a small fortune.
So that's my opinion on the matter and yes, I've worked with the F5 and Ursa Mini 4.6k, both shooting and in post. I look forward to bringing you guys some footage shot by myself and both cameras very soon.