On the side of the gaming performance Core i5-10400 surely delivers. Even though quite a few of the games start to get limited by the graphics performance (still this is 2080 we are talking about), the new model offers, depending on RAM speed, either comparable or slightly better gaming performance against Core i5-9600KF. Still AMD models are not so far behind and the overclocked Ryzen 5 3600 is even equal to Core i5-10400 with DDR4-2667 memory. The non-overclocked one is just 4% behind, and the Ryzen 5 3600X is in-between.
Another interesting factor to note is how in Metro: Exodus and Red Dead Redemption 2, there seems to be a some kind of a wall for the average framerates of AMD models, that is lower than the one for the intel models, despite the fact that all the processors in any of the subsets offer approximately similar average FPS and the load of the GPU was about maximum. This implies that there is some kind platform limitation that is hampering AMD models for displaying their full potential. One possibility being the performance of PCI Express controller for example. This might probably be also applicable to some other games, though nowhere else it as clear cut.
The things for Core i3-10100 are not going so well and it seems that the major factor for this is the halving of the L3 cache. That is most visible in our online gaming tests, where all games, except for COD Warzone, are mostly low threaded so higher core count is unlikely to be a substantial factor in performance. Also the clocks of the two new intel processors are almost identical. Still, despite that we have almost 20% difference in performance on average. So most of the time Core i3-10100 is hovering closer to Ryzen 3 3100 and Ryzen 5 2600, instead of the main group of processors. It is faster than the 2 AMD models, but not by much. On other hand it is slower than the officially similarly priced Ryzen 3 3300X and the gap is especially large again in online gaming tests, where the difference goes above 10%, and starts to get noticeable. Frankly, it seems strange to see AMD offering beating similarly positioned Intel one. And with similar cores/threads and clock configuration at that. But then again the Ryzen 3 3300X has 2,5 times more L3 cache.