You can look under System Settings, Information, OpenGL, whether there is a difference between the Intel iGPU and the AMD card.
Also in Kodi, System Information, Video with GPU and OpenGL each should be different.
And if you look up the performance of the Radeon HD8470 and compare it to the performance of the Intel iGPU (Intel HD Graphics 2500) there does not seem to be a big difference, when you look up benchmarks.
I guess older GPUs are generally not well supported and it is always better, to use more modern hardware.
Intel iGPUs, even if they are less performant seem to be better supported under linux and therefore deliver better performance than very old AMD/nvidia cards in batocera.