Although CNET did not review the LG LE5400 series, we did review the LE5500 series.
Comparing the two on LG's Web site, the 5500 has a slightly higher contrast ratio, as well as a slightly lower response time, both implying somewhat better picture quality. In practice we doubt either specification difference will make a big difference in picture quality (more info).
The LE5400 also has a "silver gray" accent to complement its glossy black, and the LE5500 is accented with "evening purple." The LE5400 series also has a 32-inch model, whereas the LE5500 does not.
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 LG LE5500 series.