RoutersOS v6 uses routing cache while ROS v7 doesn’t. While ROS6 performs routing faster in the happy-path scenario (cache hit), its performance is significantly slower in the rest of the cases (cache miss). Usually, synthetic speed tests utilize a small number of routes and, therefore, always hit the cache. However, studies had proven that there are 80-90% of the cache miss in real-life router usage. In other words, only 10-20% of real-life cases may show routing speed as high as in the tests. Moreover, there are specific DDoS attacks on routers to invalidate the routing cache and make the routing drastically slow.
ROS7 has a completely different route lookup algorithm. While ROS7 performs routing slower or/and uses more CPU than ROS6 in the happy-path scenario (usually - tests), it does a way better job in the rest of the cases (real-life usage) and is not vulnerable to the DDoS mentioned above. By the way, the latest Linux kernels also got rid of the routing cache.
And as @mducharme correctly said, CAKE is a completely different story.