Armored Core 4 has been available for the PS3 for sometime now, and the 360 demo has hit Xbox Live. There are differences, which people have latched on.
From a pinged Insert Credit and GameSetWatch's Ollie about the differences, Ollie noticed that the PS3 version has subtler heat haze effects, and while many believe the 360 demo has full screen anti-aliasing, Ollie believes otherwise. He says, rather, that the it's just the blur filter the Xbox 360 has - The XBOX had it, too.
Effects in the PS3 version seem to be hardware rendered, while in the Xbox 360 version, they are software rendered. What's more, Ollie points out that the frame-rates in both versions seem comparable (though, some people think otherwise). He adds that there are frame-rate drops in the PS3 version, but its only in two missions.