I believe that you have some facts wrong. Tab predates diet coke
and diet pepsi. Additionally there is a difference in sweeteners - tab uses saccarin while diet coke uses aspertame.
Another fact not to be ignored: Diet Coke contains caffeine and Tab is caffeine free.
On this same note, why aren’t more diet sodas using Splenda? (new sweetener, doesn’t give my wife headaches like Aspertame)
WaistWatchers soda uses it (available in the NorthEast anyway), but has no caffiene, so it’s a no go for me.
What facts are wrong? In the original column, Cecil does indeed say that Tab came first.