CNET did not review the Samsung UNES6100 series, but we did review a similar TV, the UNES6500 series.
According to Samsung's site, the main difference between the two is that the UNES6500 has 3D while the UNES6100 does not. There are also some minor picture quality-related specification differences between the two, but we don't expect them to have a major impact on picture quality. In other words, we expect the two series of Samsung LED TVs to have roughly the same picture quality.
One of those specification differences is a higher "Clear Motion Rate," listed at 480 for the 6500 and 240 for the 6100. CMR is a term unique to Samsung and while it is based on the more traditional notion of refresh rate, it's basically marketing bunk. The main thing to know is that both TVs use panels that refresh at 120Hz. The 6500 employs backlight scanning that might slightly improve motion resolution compared with the 6100, but the difference will be difficult to discern at best.
Speaking of bunk, the ES6500 also has a slightly better contrast ratio, but given its mediocre black-level performance, we don't expect the ES6100 to perform much worse. According to Samsung's specifications, the two TVs share largely identical picture quality characteristics otherwise.
The 6500 is very slightly thicker than the 6100 (0.1 inch in the 55-inch size for example) and has slightly different styling, lacking the 6100's "lip" along the bottom edge of the frame.
The two series also offer different screen sizes. The UNES6500 includes a 32-inch size and a 65-inch size, but the UNES6100 does not.
Otherwise the two series of Samsung LED TVs are largely identical. For more information, check out the full review of the Samsung UNES6500 series.