[wtallis]

I think GPU rendering was always faster as long as you had a supported GPU. Now that the Cycles renderer has support for all the major GPU APIs/vendors, the only reasons to render on the CPU are if you don't have a half-decent GPU, or if your scene doesn't fit in your GPU's memory. Neither of those are a concern on Apple systems.

At least on NVIDIA hardware, Blender can use the GPU's raytracing capabilities rather than just the general-purpose GPU compute capabilities. Which means it doesn't take a very expensive GPU at all to outperform high-end CPUs.