According to Wiki's
AMOLED page,
Super AMOLED Plus, first introduced with the
Samsung Galaxy S II and
Samsung Droid Charge smartphones, is a branding from
Samsung where the
PenTile RGBG pixel matrix (2 subpixels) used in Super AMOLED displays has been replaced with a traditional RGB RGB (3 subpixels) arrangement typically used in
LCD displays. This variant of AMOLED is brighter and therefore more energy efficient than Super AMOLED displays
[20] and produces a sharper, less grainy image because of the increased number of subpixels. In comparison to AMOLED and Super AMOLED displays, the Super AMOLED Plus displays are even more energy efficient and brighter.
However, as Wiki notes, "citation needed" to actually prove these claims.
This article from AndroidAuthority also talks about the difference.