We chose to overclock manually by raising the all-core multiplier in concert with 1.35V on the juice, up from the default 1.247V. Core i9-10900K managed a rock-steady 5.1GHz across its ten cores while the Core i5-9600K ran at 5.0GHz.
Putting that into context, the 10900K shaves 19 seconds off its default time, albeit at the cost of an extra 39W under load. 10600K's frequency increase is greater in percentage terms - 4.5GHz to 5.0GHz - leading to a 63-second reduction.
Is it worth it? Given how well the chips turbo out of the box, the answer is yes for the 10600K and arguably no for the 10900K.