These are broad statements, but the better LCDs tend to be brighter than plasma as the glass front tends to be a duller image in brighter light applications such as sunlight streaming through a window.
Why are LCDs more popular than plasma?
I have a rough time seeing differences in picture quality between brands and models, but the difference between plasma and LCD are overt even to me. When I go to bestbuy, fry's, etc. and gaze at their displays of flatpannels, plasma televisions just look beautiful, despite the reflections, while LCDs just remind me of working on my laptop. Is there more merit to the quality of LCD than I observe or is there some other reason LCDs outnumber plasmas?