Haswell handles larger DIMMs better than Ivy Bridge, so 4x4GB vs 2x8GB isn't going to make a difference at 1600MHz. As far as overclockability goes, as I understand it all of the Asus Z87 boards are going to get the same clocks on air or water in term of CPU speed, but the ROG boards will get farther on LN2/other extreme cooling and overclock memory better.