Differing cooling solutions is one of the major reasons for price differences (EVGA for example, have numerous 6GB GTX 1060's - each at a different price point). Better coolers mean at minimum, better temps - best case, they allow additional overclocking headroom.
Brand recognition play a big part though too. ASUS, MSI, Gigabyte, EVGA etc generally have better brand recognition around the world (that may different in specific locations) and can command more for ultimately the same card offered by PALIT, Gainward, Sapphire, Zotac etc.
For the average user, and 6GB 1060 will be fine - other than the founders edition cards, which have had some heat issues (which may or may not have been addressed, I'm not sure).