The 2400 CL12 will have the best performance at 2400 and the cheapest will have the lowest performance. The 2666 will probably have the overall best performance. The total contribution to your overall performance is just a few percent difference (a few FPS). You might benchmark better with one over the other but real-world differences will be negligible.
Double check all the non-performance factors -- CPU cooler clearances, color, etc. I think it will come down to if you think the extra performance is worth the extra cash.