Remember skimmers "strip" the water, not only does it take dissolved organics with it, it also takes any other nutrient in the water! So, if you are "overskimming" watch your params and keep a close eye on your animals for any indications that there is alack of "something" in the water.
I think 2 smaller skimmers are less efficient than one of equal sizes - the key behind skimmers is contact time and the size of the air bubbles. The larger the skimmer cylinder/box, the longer the bubbles can be in contact with the water/attracting proteins to the outter surface of the bubble, the better.
I am not sure the electric is as large an issue with the size of the skimmers you're talking about, but I would analyze that as cost to run is always a factor.