No doubt GPUs have the advantage, even one 1080 has way more hashpower than most CPUs, not to mention you can have bunch of them in one rig, while multi-processor systems are only on high end servers. Although Webchain officially don't support GPU mining and altered the algo to even the level, community are doing it anyway.
There are many algorithms in which even relatively inexpensive CPUs show significantly better results than GPUs.Let us see those
