wouldn't a well lit and staged studio scene where you can control the lighting not really be much of a dynamic range test and especially not at all a low light king test though??? maybe a poorly setup and lit studio shot?
A well-composed, well-lit studio shot would be nice.
Not at all.
You can easily get insane amounts of dynamic range in a scene in a studio. Just put a single light with a reflector on one side of the subject and nothing else.
And you can easily get low light in a studio; turn off the flash, turn off your working lights, and just use the modeling light of the flash turned down to whatever levels you need.
But the point is that it's all controlled, and you can easily yank the one camera off the tripod and put the other in its place, and use the exact same settings for both.
what you'd want is say some dark alley, barely there artificial lighting, model shot for the high iso and some uncontrolled, high DR landscape scene or something I'd think for the low ISO dr range comparison
Waaay too many variables. Especially in the landscape.
The great thing about the studio is that it lets you control all those -- both for consistency and
so you can create exactly the test you want.
For example, if you want to see what the camera can do with a scene with ten stops of dynamic range, no problem -- just use a single light on, say, a Rubick's Cube on a piece of black flock velvet or suspended in midair. Use your meter to read at ISO 100 and f/32 on the lit face and f/1.0 on the shadowed face, and shoot away. Take a shot at f/32 and ISO 100, another at f/1.4 and ISO 200, and another at f/5.6 and ISO 100. (Getting that level of contrast will require a studio that isn't prone to bounce and possibly a bit of creative flagging / cutting as well.)
(And the observant photographer will read that suggestion of a test and understand why the proper answer to a scene with more dynamic range than a 5DIII's twelve-plus stops can capture is not, "Get a D800," but rather, "fix the light." Or, maybe, embrace the contrasty nature of the scene, rather than fight it -- let the highlights blow and crush the blacks!)