Internally, these are the same pedal. 

Slate allowed the top surface to be re-written with a Sharpie marker; this will not work with Expanse.

The previous line of stereo reprogrammable pedals (Wet Stereo Reverb, Seraphim Stereo Shimmer, Chroma Stereo Chorus, Echelon Stereo Echo and Slate Stereo Programmable pedal) was consolidated and rebranded as "Expanse" along with a new graphic.