So I’ve done some renders and these are the results from my laptop with a Nvidia GTX 950m and a Core i7-6700HQ 2.6GHz processor:
GPU 512x512 4:40
GPU 256x256 3:40
GPU 128x128 5:00
CPU 16x16 6:10
CPU 32x32 5:50
CPU 64x64 5:30
CPU 128x128 5:00
CPU 256x256 3:30
CPU 512x512 4:30
The 256x256 render times were roughly equal for both the GPU and the CPU, but I think I will stick to the CPU. Hope this helps anyone with their choice!