I may be somewhat qualified to speculate...Based on my experience with both Intel's and AMD's OpenCL implementations for their CPUs, I suggest that Intel has a much better vecorizing compiler than AMD. The benchmarks they are running have different compilers. If it was a simple C code compiled by GCC for each CPU, the comparison would be better. It would be interesting to see the results for AMD's OpenCL compiler on the i7 and Intel's compiler on Ryzen.