Canon USA's Rudy Winston has authored an article for CPS highlighting the differences between the EOS 5Ds / 5Ds R and the 5D III.
"Current EOS 5D Mark III shooters, who may be considering moving to the new high-resolution EOS 5DS (or the EOS 5DS R, which removes the effect of low-pass filtration), may wonder if anything changed on these new cameras because the new models look practically identical to the proven Mark III camera. Rest assured, there are some new rewards waiting to greet 5D Mark III owners who step up to the new cameras. We can’t touch on every single one, but we’ll try to give an overview of many of the new details.Topics Covered
Obviously, the biggest is the move to a 50.6 million pixel CMOS image sensor – more than doubling the pixel count from the Mark III model. You’ve no doubt seen discussion of this, so we’ll go a bit more beneath the surface. Everything we discuss here applies to both the EOS 5DS and 5DS R models."
Read the entire article on the Canon Professional Services website.