My .02 cents...
I have owned bikes with both the 2 speed set up ( a 1970 and1971 Sear's Ropers) and the torque converter set-up (Rupps, Super Bronc). Performance - wise, the former are poor compared with the latter. Those of you who have had bikes with torque converters and are now thinking about doing your first bike with a 2-speed set up will be surprised and disappointed. As Mr. Donovan has stated the 2-speeds were innovative (and cool!) for their time, however, soon became dinosaurs when the torque converters came out.
Michael