In terms of picture quality, plasmas are still better than LCD sets, even the LCD/LED sets (meaning LEDs supply the back lighting instead of flourescent bulbs). Although LCD/LED sets are much better than they use to be when it comes to motion artifacts, blurring and other motion problems, such are still more noticeable with these sets than is the case with plasmas. If you sit relatively close to the set and/or you do a lot of viewing of material with a lot of motion and panning (e.g., sports broadcast), the difference between the two might be significant.
Black levels and detail in the shadows is also still better with plasmas than LCD/LED sets. The LCD/LED sets have quite high conttrast ratings because the sets can get much brighter, but, they actually cannot get quite as black as plasmas. Plasmas also tend to have more uniformity across the whole screen and can be viewed from further off axis without severe dimming. Color, particularly flesh tones, is better with plasmas than with LCD/LED sets. But, if the set will be in a location with high ambient light levels, particularly with light shining directly on the screen, the higher light output of the LCD/LED set may swing picture quality in favor of that kind of set.
Overall, plasmas deliver a better picture. Go to Best Buys and compare the two side by side, particularly with darker scenes. The LCD/LED set will look murky and have a kind of haze compared to the clearer looking plasma. But, the differences are much smaller than they use to be. LCD/LED sets have the advantage of putting out less heat (meaning also using less electricity), probably lasting longer (though either will last longer than most people will want to keep the set anyway), and is not prone to burn-in problems (burn-in problems are much less severe with modern plasmas, though you still don't want to have the same image on the screen for great lenghts of time).