1. The i-9700K CPU is newer, so it has more sales at the moment. 2. The i-9700 has no multithreading, which makes it cheaper than the i-9900K, which would be the actual successor of the i-8700K. I would only buy i-9700K or i-9900K now, depending on your budget or whether you need multithreading or not or you want the best. I'm very happy with i9700K as my application doesn't need multithreading at the moment. Somehow I should have gone for the i-9900K though, because of the future. I was looking at the budget. And now there is also i-9900KS. By the way, my CPU also runs stably at 5 GHz.