I think AC-DC must have been looking at the Airbox Foresight, whixh has a much larger screen (with corresponding price hike).
The question is really whether one wants display that shows the CAA VFR chart, in which case there is little competition for the Clarity.
The drawback is that text on a scanned chart grows or shrinks with the zoom scale, however when moving from a chart used as primary nav. to a GPS, the text is less used than the relationship to the depiction of airspace boundaries in familiar colours.