....this whole plasma versus LCD is a great debate. Up until a year or so ago the plasmas were the definite winner. It is now very close on the top quality brands.
I brought up the plasma to give him an alternative in case he had not seriously considered them. My choice is still with the plasmas, although I think many are more impressed with LCD's upon initial viewing in a brightly lighted dealers store. This is probably due to their higher top brightness level, which is completely unecessary at home unless one has an extremely bright room. Also, I think many are impressed by the LCD's apparently more detailed picture. I actually think the LCD has more of a "video" look than the plasma and do not find this an advantage unless viewing print, etc. The more "film" like look of the plasmas picture to me is a significant advantage.
As far as the contrast, you bring up a very good question. Again, the plasmas were superior in the past. But in a room with high ambient brightness as you mention, perhaps the LCD might have a very slight advantage, although I think the still superior black level on the plasma tends to prevent this. Probably no clear winner here.
Our main plasma is very near a glass sliding door and we still during the day have the brightness and contrast/picture settings way down. I think most people overcrank these settings. Our particular main plasma, a JVC, is very bright and vivid for a plasma. We have never had the slightest problem with too little brightness or contrast. These settings are always at 50% or less.
To me the most important aspect on any flat screen display is to buy a top quality brand. On many other components you can fudge a little but not on the TV.
RR6