We had used Brita filter products for many years, but then I learned about ZeroWater.  I don't remember now how I found out about it -- probably Consumer Reports or something.  I was reluctant at first, because ZeroWater filters are much more expensive than Brita.  But (a) they do a better job cleaning the water and (b) they last longer than Brita filters.  The water-quality tester that came with our countertop dispenser shows that we only need to replace our ZeroWater filter about every three months.  We can afford the price of the filters at this frequency, especially if we buy boxes of them on sale. :  )