I don't understand why you are asking about the choice. For some functions Adobe uses the GPU (e.g. oil paint filter and 3D modelling) and those functions will not work without it. For other functions it will use the CPU - for example a final 3D render will use all CPU cores.
There is an argument, in terms of color accuracy, for setting the GPU to Basic drawing mode which still uses the CPU for color management , particularly if you use the ProPhoto color space, but that is due to long standing GPU software errors rather than a shortcoming of Photoshop.