If your using the laptop for gaming, then I would 100% go for the better refresh rate over more CPU cores!
Games don't really take advantage of the more than 4 cores these days, you wouldn't even really notice a difference in gaming from 4 cores compared to 6 cores but you WILL notice going from 60Hz to 144Hz refresh rate, trust me!
Yes but the 1060 can handle a hell of a lot more than 60Hz. More CPU cores is not going to give him much of a benefit in today's games but a higher refresh rate will make a good difference. Plus if he upgrades his GPU in future, he will be able to take advantage of the higher refresh rate even more. Gaming on 60Hz sucks! Maybe go for 120Hz but price difference between both won't be much. 4 core with HT turbo up to 4GHz will blast ANY game out currently.