@disolitude
If you find yourself developing the same game for two consoles, you either develop for them simutaneously or develop for one then port to the other. We all can agree on that. But also if you decide to develop for one then port to the other, you might as well take the easier route. So if some developers finds that it's easier to develop for the PS3 first and then port to the 360 (instead of the otherway around), then that's the best route for those developers since they were planning to make the same game for the 360 and PS3 anyway.
EDIT: And I strongly expect that PS3 multi-platform games were delayed because they were being ported from the 360 version. This holds water because during the infancy of the PS3, games announced for the PS3 that were multi-platform were already released for the 360. Thus, it was developed for the 360 FIRST, then PORTED to the PS3 taking a considerable extended period before its PS3 release. It's not as common now as it was before because developers are getting a better handle on PS3 development while using the PS3 as a lead platform. Do you not see this trend?
Hackers are poor nerds who don't wash.







