G.Skill has NOTHING more too offer than any other major brand RAM manufacturer. Corsair, Crucial, Patriot and Mushkin all offer great products, as good or better as G.Skill. As for your choices, what do you want more? Speed or savings? Check the motherboard compatibility and get the fastest RAM it will support. Easy peasy.
I'll like both (speed and saving, being speed more important). But I have my doubts related to speed and timings. Some reviews show a memory 2133 CL11 having better performance that a 1866 CL8.
I take these maths:
2133/2 = 1066.5 MHz, T = 1/f = 0.94ns, t = T*CL = 10.31 ns
1866/2 = 933 MHz, T = 1.07 ns, t = 8.57 ns
So, if second one looks more fast, why the other win?