It's not just better then a standard I5 for overclocking. The non "K" version has overclocking abilities turned OFF, but the K has them turned ON. that's the only difference. even though overclocking is a pretty big deal. To me overclocking support is a deal maker or breaker. If it can't overclock, then i am not gonna buy it.
If you are not an overclocking and the non K version is cheaper, then get the non K version.
but if it's the same (or ruffly the same) price, then get the K version and buy a motherboard with an OC supported chipset.
OC enabled chipsets does not cost more. You never know if you are gonna end up overclocking anyway.
MOBO: Asus Maximus 6 Hero - GPU: Gigabyte GTX 980ti xtreme - CPU: I7-4770K - PSU: Corsair AX760
RAM: Corsair Vantage 2x4GB - SSD: Samsung 840 Evo 512GB - Case: NZXT H440