Rendering Flops or Shading Units

For Rendering with Cycles and other render engines (eg. V-ray, Octane etc)
Does the Flop amount matter or the number of Shading units or CUDA units

Having a high Flop amount should affect the redering much more right ?
Or is it better to have a high GPU core amount ?

Cores have pretty much nothing to do with anything… If nvidia makes a GPU with 256 cores and they are 20x faster than the Maxwell cores the new ones will win just because they can do more per core. Core count is just a number.