Eng cameras have a better form factor - more of a all-in-one system rather than having to "put together" a camera with 3rd party attachments, rigs etc. 2/3" chip gives you more depth of field that with long lenses you wouldn't have to chase focus between one eye versus the other as much as a s35 or vistavision formats. This is of course my opinion. I used to operate Betacam cameras for example and it was great operating those cameras. Well balanced and all inclusive camera without cages etc. Hand held to sticks you don't have to reconfigure anything. I am not suggesting a Betacam but a 2/3 inch HD ENG camera with same type of body - the high end ones not the basic good enough for news gathering types. For analogy sake, uvw 100 versus Ikegami hl59 W or sony d600 - sure all is Beta SP but the 100 was the cheapest versus 65k 600 or 59w were not the same at all in terms of colors, dynamic range etc. 100 was straight up good enough for news gathering and some other low profile work. Pair it with a nice long HD ENG lens with a servo and you're set. Red etc is not very practical for documentaries unless you're shooting about the pyramids etc. People nowadays seem to care about how their "rigs'" look with matteboxes etc to imitate cine cameras . You don't need any of that. Those cameras have internal nd filter selection so just regular lens shade that screws on the lens is fine. Don't buy into the idea that you need follow focus etc. We didn't use any of those configurations with Betacams for docs. Practicality wins imo. The last thing you want is to deal with 3rd party rigs etc in an environment like you are going to be working. Mind you most of those people don't even really need a follow focus or mattebox but hey it looks cool i guess. Also the ENG cameras have onboard sound too. Betacams had Dolby 2 ch or 4ch depending on the vtr with proper 3 pin xlr ports and monitoring display and dedicated sound adjustment knobs etc. And the viewfinder placement in relations to its shoulder pad is perfect too that you don't have to fight the camera which is crucial if you are serious about operating. Watch Nat Geo or Discovery wildlife docs... They are shot on these types cameras mostly. It is practical. And the camera has some mass to it for Christ's sake that it doesn't show shakes etc, which at those long lenses, even on sticks, it gets pretty touchy. I don't get why the craze about awkward brick style bodied cameras. I prefer to operate heavy but well balanced full size cameras for example. In other words, it is a ready to go all in one camera for these types of applications. If you're shooting drama then sure get the RED. Hope it helps.