It all depends on your needs as the K and non K chips aren't 100% identical. For instance, K series chips lack VT-d support. If you're planning on using VMs a lot and not planning on overclocking then a K series chip is worse off than a non-K. Basically, it all depends on your needs and what the chip offers. But a K isn't the same as a non-K with the ability to overclock. Intel doesn't like to make anything that easy
Keep in mind that if your CPU roasted due to a failure of the stock fan when properly installed Intel would be obligated to replace it for you as long as you purchased the retail chip. Intel gives all of their retail chips a three year warranty. As a result, I'm sure the stock cooler is more than enough unless you have needs that extend beyond that (overclocking, quieter operation, etc.).
I'm surprised it took this long for anyone to mention this. The K version lacks features and processors are plenty fast these days to eliminate the need to overclock unless you're doing it for fun. the default choice should be the non-K version.