I have just bought an Asus P9X79 Delux MB. I intend to go for 32GB ram, would I get better performance from 4x8gb modules (this would allow me to expand in the future) or 8x4 gb modules that would use all the slots? This is for Premiere CC and a bit of AFX.
Logically speaking, there should not be any difference in performance, because each bank of 4 slots is electrically separated from the other and the bank(s) is completely populated, so the quad channel architecture is fully used. There may even be a slight overhead when using two banks, because of the traffic cop who directs traffic to bank A or B. For expansion reasons, I would opt for 4 x 8GB sticks.