I have previously worked for both Sony and Samsung so I know the two panels. The Samsung panel is quite noisy and doesn't quite live up to the colour gamut in the XBR.
But hey, if the extra 3 inchs real estate means a lot to you, sure go the Samsung. These two panels are about as good as you get in a large LCD unless you dont mind waiting and paying an arm and a leg for O-LED. Wouldn't hold my breath on when O-LEDs that large are due out though.
I'd say Samsung. In my opinion, Samsung's price-quality-equation is much better, meaning they're better value for money. If you strictly look at picture quality, though, you should probably go for a Philips tv.
...go to the store and have them put the two you like next to each other with a splitter to the SAME video source so you can see how they react to the SAME video source...make sure the TV's are set to the default settings and then you can adjust from that point... happy hunting...