Hi all - I have narrowed my new PC search down to two both of which have almost identical specifications - one has an Intel Corei7 Eight Core Processor i7-9700K (3.6GHz) 12MB Cache and the other has an AMD Ryzen 9 3900X.
Which would you choose?
Mainly for Flight Sim 2020 later this year.
Firstly, I agree with @Oussebon
that if you are purchasing this computer primarily for the purpose of playing Flight Sim 2020, I strongly recommend waiting until the game is released. Once we have professional benchmarks of the game you'll be able to make a much more informed decision on what hardware you need. If you buy now in anticipation, you run the risk of either being disappointed in the level of performance you get, or going the other way and spending a bunch of money on hardware that turns out to be overkill.
With that out of the way, I do still want to answer your question. If those two PCs are identically specced apart from the processor, then the Ryzen 9 3900X is a pretty objectively better choice. The i7-9700K is an 8 core / 8 thread processor. The Ryzen 9 3900X is a 12 core / 24 thread processor. While the i7-9700K can eek out a few more FPS in games that favor the fastest possible single-core performance, it's a narrow lead, and the Ryzen 9 3900X is on a completely different plane of performance when it comes to highly threaded workloads.
If you had to buy this computer today, the Ryzen 9 is the better choice, but I'd wait for Flight Sim 2020 and to come out (and the new computing hardware that will release between now and then)