[citation][nom]Vladislaus[/nom]Because perhaps Samsung doesn't want people to know that it has the same GPU that's in the S II.[/citation]
The International version of the SIII has a Mali-400, but the chip in the SIII is clocked at least 50% higher than what's in the SII. Anandtech has benchmarks up, if you're curious, showing the SIII as the most powerful current smartphone in graphics benchmarks... the International version is, anyway, with the aggressively clocked Mali-400.
The US Version of the SIII will probably be the Qualcomm S4 SOC with the Adreno 225 on it... and perform identically to the AT&T HTC One X tested. Which, ironically, is about the same level of graphics performance seen in a Galaxy SII.