Progressive 2bbl

Wrote to Redline/Weber concerning swap. They are steering me towards the DGAS which is a "synchronous two-barrel". They say is has more of a "Wow factor". At $3.75/gal here at the edge of the world, I'm not looking for a whole lot of "Wow". WTH? Isn't a BBD a synchronous 2bbl? Can someone explain?