Product review (5 stars): These are the best.
I've tried less expensive filters in my Vornado Humidifier (the ones NOT made in USA) and there IS a difference.  These fit perfectly every time without fiddling or pushing, have a longer life between changes and offer, nearly, twice the output as the "off" brands.  Definitely worth the few extra bucks you pay.

That's all I've got, but in all fairness it's difficult to wax rhapsodic about humidifier wicks.