Drain fed skimmers work more "efficiently" because all of the "dirty" water goes through your skimmer before going anywhere else.
I have a friend with a drain fed skimmer with a recirc pump. The recirc pump doesn't even have a venturi or anything on it and just chops up the bubbles that come from the drain. You won't believe the skimmate the thing produces. In fact, it actually skimmer out an entire fish!!
(fish went down the drain into the skimmer and got skimmed out).