The Mitigation Impact Difference On AMD Ryzen 9 3900X vs. Intel Core i9 9900K Performance
While all these tests were with SMT/HT left enabled, in some of the heavy multi-threaded tests like V-RAY and Blender were slight differences when running without the security mitigations particularly with the AMD Ryzen 9.
Most of you probably aren't running Memcached on your desktop CPUs, but its performance was lifted up by booting the Linux kernel with "mitigations=off".
Intel delivered better web server performance over the Ryzen 9 3900X with Apache when disabling mitigations.