Ricoh GXR GR Lens A12 28mm has a
12.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features GR Engine III processor. On the other hand, Ricoh GR II has a
16.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor and features GR Engine V processor.
Below you can see the GXR GR Lens A12 28mm F2.5 and GR II sensor size comparison.
Ricoh GXR GR Lens A12 28mm and Ricoh GR II have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.