It is apparent that some do their homework more than others. I have spent more time than I would like to admit researching this and I am a system engineer that does IT for a living. I almost made a similar mistake of going with the 8700k over the 8600k. Luckily additional research showed that the 8600k was superior for me.
It is easy to say the most expensive thing is better, though it is not always the case. First off, you CAN'T manually overclock a non-K processor. So if you plan to OC, then don't get the 8700 non-k. If you are using your PC primarily for gaming, than the 8600K is hands down the best CPU for you as well as value. Based off the voltage required to get identical overclocks on both the 8600k and 8700k on silcon lottery's website. There is proof that the 8600k is nothing more than a stocked nerfed 8700k w/ less cache and no hyper threading. These differences go away when you overclock:
-As of 12/01/17, the top 72% of tested 8700Ks were able to hit 5.0GHz or greater.
-As of 12/01/17, the top 84% of tested 8600Ks were able to hit 5.0GHz or greater.
-As of 12/01/17, the top 3% of tested 8700Ks were able to hit 5.3GHz or greater.
-As of 12/01/17, the top 13% of tested 8600Ks were able to hit 5.3GHz or greater.
sources:
https://siliconlottery.com/collections/coffeelake
So by this token the 8600k is a much better overclocker and more games and applications will hands down benefit from a the raw performance of added frequency and 6 core count. Frequency and Cores will give results, though Hyper threading only gives you a smaller margin of improvements and that is for specific applications. i.e. rendering, synthetic benchmarks, 24/7 hosting of VMs, and other non-gaming applications. In the server world a lot of systems sit idle, those benefit from hyper threading a lot more than most user level. In the future as more CPU intensive games, your system will use more and more of your CPU. As most games fall out of popularity quickly, I don't see any reason for developers to optimize their games for hyper-threading. Then take into account the amount of gamers who use I7s vs I5 and I3s. Then look how SLI/Crossfire is not as widely supported as it use to be. Even if games are optimized at a later date for HT, then HT still doesn't give you the same return like additional cores do. I do host a couple of VMs, though I don't run them 24/7 and I don't have them running when I am playing games.
Additionally as odd as it is, the 8700k, 8700, and 8600k all have varying base and boost frequencies.
I went with the 8600K and Gigabyte Gaming 7 motherboard for the better VRM for overclocking. I was able to get this combo for ~$440 ($300 CPU + $210 Mobo - $20 MIR, - $50 Combo deal). Then I used my Citibank pricerwind feature and saved another $70 making it $370 for this $250 mobo and $300 cpu.
Again it all comes down to your use and 95% of people who buy the 8700k, would be better off with the 8600k.
. Bom, talvez seja trauma meu com i5: tive o i5 7400 e não tinha um dia que não pensava: "porque não comprei i7 ?????"
, tenho procurado sempre comprar custo x benefício... 
