More complex PoW, such as a memory hard one requiring several GB of memory to solve efficiently, can lower the efficiency gap between GPUs and ASICs to about on

More complex PoW, such as a memory hard one requiring several GB of memory to solve efficiently, can lower the efficiency gap between GPUs and ASICs to about one order of magnitude, but not much less. That means that ultimately, only ASICs can mine profitably (and only if they have access to very cheap power).