I think the Sony's have the potential to be better in both input lag and motion resolution. If you just care about input lag, the Sony's are proven very good. The F8000 has user reports of great input lag, but it's hard to test that out yourself since most stores won't update firmware. If you really like the F8000 and really care about input lag, I would wait for more testing.
If you care about motion resolution, I recommend you try them out. Impulse mode is not for everyone. You need to tweak the light output / contrast settings to extreme levels to get a bright enough display with Impulse mode. Also some folks see the flicker more than others. And it really requires 60fps game to benefit. It's a unique feature of the Sonys, but a bit quirky. I really recommend you test it out on a game you care about. I usually bring my own laptop into the store and run a game that I know i can lock at 60fps. I test with both first person shooter games, doing fast panning, and also 2d isometric games (Diablo) and do full screen panning.
For me I care way more about motion resolution than input lag, since I don't play multiplayer competitively. But gaming is only part of the equation for me personally.