The fact they are distinguishable on many letters is why the quest exists. See http://typewar.com/stats/typeface_pair/Helvetica_Neue/Roboto/ http://typewar.com/

The fact they are distinguishable on many letters is why the quest exists. See http://typewar.com/stats/typeface_pair/Helvetica_Neue/Roboto/ http://typewar.com/stats/typeface_pair/Helvetica_Neue/Roboto... for what letters people find easy to distinguish and not so easy.