Source: EGM^2 – Issue Number 7 – January 1995
The Super Advantage by AsciiWare is just what it sounds like. A newer version of the original Advantage joystick for the NES but for the Super Nintendo instead. These arcade like joysticks were better for certain types of games (fighting games for instance), particularly for a more arcade like experience.
The Advantage had been developed by Nintendo for the NES in 1987. I’m not sure exactly when the Super Advantage was released but this ad is from the January 1995 issue of EGM^2 so my guess it was released in time for Christmas 1994. In addition to more arcade like controls, it offered turbo and other features. I’m not sure why they opted for four buttons on one row and two buttons on the other instead of a more typical 3/3. The original SNES control pad has six buttons also but two of them are shoulder buttons so maybe they were just trying to separate them in a similar manner.
You had to really want one of these to get one. They were quite expensive for the time though well constructed. If I recall correctly, they were something like $59.95 when first released. In the case of the Super Advantage, Nintendo decided to license it out to AsciiWare, who made a number of other peripherals, instead of selling it themselves.