There’s a big difference unfortunately in the GPU DDS conversion tools (that are Nvidia only, as they use something called the CUDA library for those graphics cards) and a CPU-only way that the Mac tools use. The biggest constraints would be CPU clock speed followed by I/O speeds (basically how quick is your disk, SSD helps).
It might be worth just trying your own Ortho creation @Lon - or at least make a small area using Bing etc and then compare speed of that vs extracting these pre-baked ones. Info on that here: