In terms of software there is only one major precedent so far (i.e. a major PlayStation franchise that is now multiplatform), and that's DMC4, which has sold more worldwide on PS3 than on 360. Going by this single piece of evidence, since it is the only relevant one we have, it certainly looks as though the game will sell nearly as well on PS3 as on 360. Obviously, there will be a greatly reduced Japan factor, while the much greater popularity of GTA will make installed bases more important, so there is no doubt that in the short term at least 360 will sell more software, but there is no reason to believe it will be even close to 2:1.
As for hardware, the beast that is GTA is what will make people go out and make a decision, but that decision will be determined by the other games around GTAIV, and in my opinion MGS4 and the recently released GT5P will lead most to opt for PS3. At the very least this situation will obtain for Europe. It may be different in the US, but in that case its plausible that we will simply see a continuation of recent trends but on a much more bloated scale, i.e. PS3 ahead ww but not by much.







