The Crane is best suited for Mirrorless cameras, & becomes less responsive when over-loaded. There are other single-handle gimbals that can handle the weight of a 5D3, & lenses such as the 16-35mm f/2.8, but likely require learning SimpleBGS software to realize best performance. The lure of the Crane is how easy it is to use without learning SimpleBGS.
Whether you'd be better served by a single, or dual, handle gimbal depends on your needs. Dual-handle gimbals can support accessories such as remote focus/zoom, mattebox, audio, dual operators, etc, but are harder to transport, & take longer to build, plus are more difficult to use in a confined space/crowd, or hang out out a car's windows. There are numerous shots I know I could not have gotten with a dual handle gimbal, but just as many where a Movi would have been the better choice, so there's an argument for having both.
Whatever type of gimbal you decide best suits your needs I suggest choosing a version that incorporates encoders.
There's a discussion about the Crane in the News section of the forum.
You don't want to run a 5D MKIII on a Crane. It'll be sluggish and overloaded. I am running the 80D, which is a lot lighter than the 5D MKIII and even I can only use certain lightweight lenses. Plus the arms will be so extended to balance that heavy a load that many of the 360 movement will be restricted. The Crane is designed for the Sony 6300 and cameras like it. Running a DSLR on it isn't the best choice, I'll be moving to the Fuji XT2 next year with it. Movi 5 or a Letus Helix Jr./Ronin M would be better choices for a 5D MKIII but focus is going to kill you. Damn FF sensor makes shallow DOF even with WA lenses and you have no video autofocus. 5D MKIII is not an optimal gimbal camera anyway, get something with DPAF like the 70D/80D or a mirrorless with autofocus.