When in the optimized modes and with optimal sample rate and phase, the OSSC discards samples to effectively keep only those that fall on the center of the pixels in the source. The resulting samples are then repeated to form the output resolution.
In the generic 4:3 mode however, the OSSC does not discard any samples. This means it captures the transitions between pixels in the source. This result in a softer picture, where the softness is determined by the bandwidth of the source signal.