Well most recirculating skimmers are needlewheel skimmers. They both use the same 'type' of needle wheel pump to produce the air bubbles. The standard needlewheel skimmer (I.E. Euroreef or ASM) use a needlewheel pump to pump water into the skimmer tube.

A recirculating skimmer works a little differently. Most are feed through gravity (from a drain line from a overflow) or can be feed by a seperate feeder pump. Once the water is inserted into the skimmer tube, a needlewheel pump mounted to the side of the tube takes the water, injects bubbles into the water and then re-enters the skimmer tube. More expensive recirculating skimmers will use multiple needlewheel pumps to give you those fine, tiny bubbles.

Typically a recirculating needlewheel skimmer will cost you more.