Although CNET did not review the Samsung UND6050 series, we did review the UND6400.
Comparing the two on Samsung's Web site, the main differences include 3D compatibility and styling. The less-expensive UND6050 is 2D-only and can't display 3D images (more info) and also has a thicker bezel around the edge of the screen. Comparing the two televisions' dimensions implies that the UN6050's bezel is 0.6 inch thicker than that of the UND6400.
The UND6050 also has a "clear motion rate" of 240, as opposed to 480 for UND6400. These numbers are derived from the TVs' refresh rate and as such should have minimal impact on picture quality.
As far as we can tell there are no other major differences between the two series. For more information, check out our full review of the Samsung UND6400 series.