They both fit the SS114 elongated seat. Bowl dimensions are the same.
The II series is at 16-1/8" height, which is 1.5" higher then the standard height Ultramax.
The S series uses 1.6 gallons, vs the 1.28 gallons of the E series.
If you feel the need for more water, holding the handle down at times will give you that extra amount.
The II or maybe I should say C series uses cyclone rinse. It swirls the rinse around the bowl, instead of the straight down rinse of the original.