I would also count the resale value of the GPUs in the roi calculations, as they will still hold their value pretty well 2-3 years down the line. That being said, AMD cards might not be a good long term investment seeing monero changing algo and eth changing algo and going pos in the near future.
I prefer NVIDIA rather than AMD, and that's indeed the advantages of choosing GPU because there was only a little decrease in its value after being used for some times.
Horrible price for second hand of ASIC when we are using ASIC to mine crypto but ROI will be even faster than GPU.
But as per POS transition of ethereum and that may become the worst thing for me to shift my mining rig to another coin.