In the words of Greer:

The Southland Harmonic Overdrive is built on the Lightspeed Organic Overdrive platform, we have developed what we believe to be the best overdrive on the market. The Lightspeed was built with the specific purpose of being a light to mild overdrive. The Southland is the next logical step for the Lightspeed platformmore gain, with two stages of clipping (utilizing different diode types for each stage of clipping), a focused midrange (not that annoying hump), and a bit of presence on top of the signal, to help cut through the mix. The Southland Harmonic Overdrive, like the Lightspeed, is touch sensitive, responds to pick attack, and has dynamics that just wont stop. On top of that, weve selected a chip to drive the Southland that takes it to the next level.