2x16GB will be a little less stress on the MC and depending on the stick, some are higher performance. i.e. Gskill has released sets of 2800, 3000, 3200 with a CL of 14 in both the 2x16GB as well as the 4x8GB for 3200. I had a 4x8GB 3200 and grabbed a set of the 2x16GB 3200/14 which was better than 4x8GB and have since gotten a pair of the 8GB sticks to play with the 16GB ones so 48GB total