Update: We now got the answer to this little mystery, you can read it here.
Samsung's new Galaxy S2 phone has a Super AMOLED Plus display but something is strange about the resolution of this phone. It's a 4.3" panel with 800x480 resolution (WVGA). That's the same resolution found on the original Galaxy S that has a 4" Super-AMOLED. When Samsung announced the Super AMOLED Plus they said that it offers 50% more sub-pixels and offers over 300ppi.
The original Super AMOLED used Samsung's PenTile Matrix scheme (shown above on the right) - which uses a shared green pixel (RGBG). The Super AMOLED Plus displays uses a regular RGB matrix (shown above on the left). That means that you need more subpixels to show the same amount of pixels - indeed a pentile matrix uses 33% less pixels (for example a 4X4 RGB display will use 48 subpixels while a 4X4 RGBG pentile will use only 36 subpixels).
But still: the new displays should offer 50% more subpixels - so even a same sized display should have had a higher resolution (about 17% more). So what's going on?