The SD-1/808 has a lot less distortion available, with a smoother, warmer sound that can get quite clear. It has a lot of midrange. Pretty much a tube screamer sound, with a clean amp it does not add a lot of distortion, but with a cranked marshall it's enough for Monster Magnet's thick Sabbath type tones.

The DS-1/Super or Pro have more distortion available, a crunchier sort of british sound, but still are VERY clear sounding. It can get quite clean too as it has good picking dynamics and cleans up well. Does not have the midrange boost of the SD-1 tube screamer type pedal. Even with a clean amp, this pedal can get quite a good amount of crunchy distortion. The DS-1/pro also has stronger low end than the SD-1/808 or other tube screamer based pedals.

Here is a page where someone tried a DS1/pro and sd1/808 in combination and described the various sounds in different orders and settings - bosscombo.htm.