I would imagine the recirculating are "better", but what it does is has an external pump that feeds the water into it, and then another pump for the actual skimming... Could produce more heat transfer, and are just more to have to deal with... The NWB has 1 pump for intake and skimming. Much easier IMO
and just as effective on a smaller tank like a 75. I think the recirculating ones are better for bigger tanks, and can skim more water due to the external pump pushing water through, not too sure though on that.