Create ML Training Speed CPU vs GPU

Hello,


I'm currently working on a project that requires the usage of the Create ML tool to create the ML model for an application. I've managed to create a CoreML model with Create ML, but the training time takes around 65 hours to complete.


For reference, I'm using a 2018 Mac Mini with i3 CPU. Using an external GPU is certainly faster than using CPU, but for how much faster? I don't want to spend USD 1000 on an external GPU config only to only reduce the training time by small amount. If the speed increase is significant, what is the GPU recommendation to use?


Thank you in advance.