The base difference is that batchPro created a batch file then ran it. This version only creates a batch file without running it. It has allowed me to do a mod on the design, but adding a cpu thread count option so that the ffmpeg can be optimised by working out the number of threads that best suit a particular CPU.
By default, ffmpeg allocate all threads and while it works, it does not seem to be the most efficient way to perform the task as at least in some instances, reducing the thread count rom the default "all" improves the time for multiple files.
A factor that matters is the ffmpeg version you use in Windows. If you go to the following site link, and download this version, its a lot faster and less demanding on the CPU, basically the holy grail.
https://github.com/BtbN/FFmpeg-Builds/releases (https://github.com/BtbN/FFmpeg-Builds/releases)
Some unusualy effects, the time on a collection of MP4 files that I use for testing dropped rom just over 10 minutes to 5 and a half minutes with the threads set to 8 on my old i7. With this version the Xeon's I have set up could be tweaked to run at the same speed.