Sharp is better than the Samsung - had GD1, now using R41. Not quite night and day difference, but enough to see the Sharp was a better design. How much improvement the GA 6 has had, or how close it'd be to the GD1 (last year's model replaced with GD7), I can't say, but I'd be surprised if it wasn't at least the equal to it.
As for PC usage - IIRC, the Sharps do 1360x768 - so a slight bit of stretching to fill the full 1366 width.
Adjustable backlight makes enough of a difference to be worthwhile having. The Samsung doesn'd have that function, and can be trickier to nail the adjustments to get as good an image as the Sharp did.
Again, the GD1 had adjustments by the bucket-load, but have of them were not touched, and I got an image I could've lived with forever and a day.