Unfortunately not all application will benefit from either higher clock or lower latency; still, I'd recommend getting the 1600 since the timings are already tight on that kit.
If you planning to OC your RAM, since the 1866 has a XMP profile for higher clock, then this one can be a good investment. Usually GSkill kits has Hynix chips inside, and they are great chips for overclocking, and can actually be overvoltaged if need be (depending on the motherboard as well, of course). The reason is that sometimes you need to add more voltage if you want to hit tighter timings. Some 1866 modules can go for 8-9-8-28 at 1.65v, for example.
For everyday usage, the differences are not great. You can observe this if you're 7-zipping gigabyte-sized folders, running virtual machines, or compiling your own kernel, for example. With higher clocked kits you will have a slight edge, but for gaming, it's practically negligible.