Fujifilm Real 3D W3 has a
10.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features 3D RP(Real Photo) HD processor. On the other hand, Fujifilm X20 has a
12.0MP 2/3-inch (8.8 x 6.6 mm ) sized CMOS X-TRANS II sensor and features EXR Processor II processor.
Below you can see the Real 3D W3 and X20 sensor size comparison.
As seen above, Fujifilm X20 has a 2.1x Larger sensor area than Fujifilm Real 3D W3. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.