Intel’s decision to arm its Core i7 line-up with eight cores makes sense, given a new eight-core, 16-thread Core i9-9900K flagship. But of course, the company had to pare its Core i7-9700K back to keep it from nipping at the i9-9900K's heels. Gone is Hyper-Threading, along with a bit of L3 cache. Nevertheless, two extra cores, higher Turbo Boost frequencies, and solder-based thermal interface material all combine to facilitate better performance in lightly- and heavily-threaded workloads compared to Core i7-8700K.
In the chart below, we plot gaming performance using average frame rates and a geometric mean of the 99th percentile frame times (a good indicator of smoothness), which we then convert into a frame-per-second measurement. Bear in mind that we tested with a Nvidia GeForce GTX 1080 at 1920x1080 to alleviate graphics-imposed bottlenecks. Differences between our test subjects would shrink at higher resolutions.
As you can see, Core i7-9700K and Core i9-9900K are very similar when it comes to gaming. You certainly wouldn’t notice a difference between them in the real world at 2560x1440 or 3840x2160. Intel's Core i7-9700K certainly has enough horsepower to push the fastest graphics cards available. Saving a bit of money by skipping the -9900K, the expensive motherboard you need to drop it on, and super high-end cooling should help fund a better graphics card.
Intel’s Kaby Lake and first-gen Coffee Lake processors excelled in gaming benchmarks and lightly-threaded application workloads due to compelling per-core performance. But the arrival of AMD's Ryzen forced Intel to reconsider its strategy. Ryzen’s big core counts and inclusion of simultaneous multi-threading translated into substantial advantages in parallelized tasks. Today, Core i7-9700K's eight cores and aggressive Turbo Boost frequencies narrow the gap. Ryzen 7 2700X is still a great CPU for heavily-threaded applications, but its lead isn't as large. Moreover, the -9700K maintains a commanding lead in single-threaded apps, making it a well-rounded performer.
The Core i7-9700K’s extra on-die resources and higher multi-core Turbo Boost frequencies are enabled by Intel's solder-based thermal interface material. This STIM also helps relax the chip's cooling requirements, making it possible for a heat sink and fan to handle stock operation. High-end closed-loop liquid coolers should provide enough headroom for most overclocking efforts. And unlike Core i9-9900K, you don't need to sink big bucks into a premium power supply.
AMD's Ryzen 7 2700X remains competitive, particularly in measures of performance per dollar (value). Core i7-9700K is faster in games, but again, the 2700X should provide a similar experience if you match it up to a mid-range graphics card or run at the high resolutions that bottleneck even top-end GPUs. Ryzen 7 2700X is also attractive for builders with limited budgets, who want to spend the money they save on a gaming card on the higher-end of the GPU hierarchy.
Core i7-9700K doesn’t warrant an upgrade if you already own an -8700K or even -7700K. But if you're building a new PC, there's no reason to compromise by seeking out the older Core i7-8700K. To be sure, Intel's Core i7-9700K is the new mainstream performance leader for enthusiasts with money to spare. If heavily-threaded productivity applications are commonplace on your desktop, there might be reason to invest in Core i9-9900K. Otherwise, avid gamers and overclockers will find Core i7-9700K to be a well-balanced chip that doesn’t disappoint.