There's relatively little difference between the two when it comes to gaming*, but the kit running at 1866Mhz is the better of the two. This is because of the increased speed (1866 as opposed to 1600), which is more than enough to offset the slightly looser timings (the 9-10-9-27 part). But really, the difference in the vast majority of games will be negligible.
*I'm talking about gaming with a discrete GPU here. Integrated graphics are a whole different kettle of fish, and benefit considerably from faster RAM.