The trouble with evaluating the performance of a television at Best Buy is that the lighting environment in the store is, probably, nothing like your home viewing conditions. Most people don't watch their television primarily under direct fluorescent lighting, so for home viewing you typically don't need (or want) a high brightness level from your television. Additionally, unless you took the time to look through the menu settings on each television, you don't know if the two televisions were configured to similar brightness, contrast, and color temperature levels.
The eye tends to be drawn to a brighter display at first glance, particularly in a retail setting where there are many televisions on display. But, the brightness of the picture has very little to do with the overall quality of the display. The picture characteristics that have the biggest impact on your viewing experience tend to be contrast with darker content (if a movie has a dimly-lit scene, will you be able to see the details?) and motion handing (does the television display motion smoothly, without blurring or other artifacts?). While a bright television may seem impressive at first glance, it is these latter characteristics that tend to determine whether your viewing experience is satisfying over time. Black levels and motion handing happen to be the areas where plasma televisions have consistently excelled relative to their LCD counterparts.
The only time that the brightness of the television becomes a more important consideration is if a significant portion of your viewing takes place under bright lighting conditions. For me, as an example, most of my viewing is at night, perhaps with the exception of football on Sunday afternoons, so absolute brightness of the panel isn't very important; quite the opposite: watching a bright television under dark lighting is fatiguing and doesn't provide the best picture, so my current television isn't set even close to its maximum brightness level. I have an older Hitachi panel, and it actually has "Day" and "Night" modes that allow me to have two different picture setting presents that can be toggled from the remote, recognizing that you probably don't want the brightness on the panel to be turned up as high unless you're watching the set under brighter lighting.
If you do a lot of your movie-watching or gaming in a bright room, then the brightness of the panel may be more important for you, but even then, I'm not sure I would give up the television that has the ultimately superior picture quality under controlled lighting just to get somewhat better performance under bright lighting, when I would likely do my most "critical" viewing under controlled lighting. Put another way, unless bright lighting is my primary viewing condition, I would put up with diminished performance under bright lights in order to get the best possible picture I could have under controlled lighting, when I'll likely care more about how the picture looks. Continuing with my example, I like the picture to look good when I'm watching football and the sun is streaming in the windows, but I don't care as much about how the picture looks for afternoon football games as I do when I'm watching a movie at night. I would want to have the television that performs best when I care about the picture the most.
Edited by marvin4653 - 11/10/13 at 10:01pm