[nevcairiel]

dav1ds AVX2 is fine. If you want to properly compare SSSE3 vs AVX2, then you need to look at Single Threaded benchmarks. Multi-Threading is often limited in scaling, where such differences can "hide".
But you should also not expect twice the performance from AVX2, since once you optimize everything possible with SSSE3/AVX2, the remaining parts that cannot be optimized so easily will impact the performance the most.