The XBR8 uses the exact same panel as the Samsung 9. However, there are differences. I've heard their LED lighting is better. Their default color scheme is a tad more natural than Samsung's. Their frame interpolation feature (SmoothMotion) is better than Samsung's Auto Motion Plus, though I don't like that feature on ANY set available today.
Get the Sony if you have to absolutely have the best. Get the Samsung if you don't use frame interpolation (the main 120hz feature, aside from 24P), and want generally comparable quality for about 20-25% less cost.
The Samsung you've posted is an entire class above the Panasonic. If you are getting this TV strictly for gaming, and are willing to drop the extra coin (~$1000 more) definitely spring for the Samsung. Its hard to go for a 60hz tv after seeing 120hz in action.
Pretty much what I posted in my first post. If he's using a Samsung 9 to represent the LCD, he should be using the best Plasma as well, the Pioneer KURO Elite, and not a Panasonic