I said previously that measuring the time from black to white to black again is slower so it should be compared to other displays that use the same method. Ditto if they use gray to white to gray as the method to measure it.
You must compare apples to apples or know you are not comparing like measured displays. Which is more accurate? Since all things in a moving picture CAN have black in it, I would think that black to white to black is more representative of real world use myself.
You will have to research HOW LG measures that spec and then compare to other displays that measure with the same method to know which is faster.
It really is too bad there cannot be standards required for the mfg to follow here, but AFAIK there is not.
EDIT:
This is WHY you cannot just accept the specs on retailers web sites:
http://us.lge.com/products/model/detail/tv|audio|video_lcd%20flat%20panel__32LG70.jhtml
Under the specs tab for this display at the mfg site it says the response rate is 6.5ms and they say it is using G to G which is gray to white to gray. Using that method means it is overstating the speed based on my reasoning earlier in this post.
You need to check the mfg site for your model number you are interested in to find HOW they measure response times and what it truly is.
