One week all versions is the identical.
One week the PS3 version is superior because of bluray, and 360 will have the inferior version, because it's to expensive to ship it on X disks.
One week, it's to slow rasterizer on PS3 so now the PS3 version will be the inferior again to the inferior 360 version.
None of this is actually true if you read the interviews with Carmack. This is just the common talk that floats around on forums.
He's always stated that they will be extremely similar but with some differences to because of the strengths and weaknesses of each platform. I haven't heard him say a particular version will be "better" just slightly different because of different storage, memory etc.
Carmack didn't seem to like the PS3 architecture, and maybe he still doesn't, but he's not a fan boy. If he makes a game on any platform, he's going to try his best to make it as good as he can. I don't think any of the platforms will be left behind.