Take with a grain of salt!
VGChartz.com | News
They say GTA4 sold an estimate 2.5 million copies in the US alone, in 1 day.
They say that in the America's, 60% of the copies were of the 360 version, and 40% were PS3. While in Europe, it is the exact opposite out of a total of 1.7 million units.
So this is a total of 4.2 million units in 1 day.
To sum it up.
-Sold better in America on the 360
-Sold better in Europe on the PS3
-Attach rate is better on PS3
-Total of 4.2 million units
-Will probably outsell Halo 3 in a few weeks. :p
-Vgchartz is not a reliable source
But the would America and Europe thing seems very reasonable. Europe has always been known as more of a Sony territory. While current the US is more about the 360.