That is a pretty interesting review. Annoying that the tester is using total dissolved solids as a metric. There is nothing bad about total dissolved solids. The main thing that I learned is that I am not comfortable drinking water filtered through the Zerowater. It would be really interesting to see the alkalinity of the water after filtration through the Zerowater, the pH was much lower and I would want to know why. It isn't fair to put the RO beside gravity filters because RO uses electricity, also RO specifically adds TDS because it isn't safe to drink water with zero minerals in it.
Illuminating also, that the iron test added iron vitamins, a good indication that iron isn't harmful or even undesired in drinking water. Iron is an issue because it might have a taste, otherwise it might effect appliances which a gravity filter isn't going to address.
And that is the main point of these filters, taste. Really the filter that is best for aesthetics is the one that results in the water you like best from the source that you are using.