I've got both ps3 and xbox too, the service is about the same. I don't usually use cross game chat on xbox, but that's because I play solo most of the time, and I don't have as many friends on xbox as compared to ps3 :/ Plus go to this link:
You must login or register to view this content. It was posted by josh olin, so I'm pretty sure its accurate. It confirms splitscreen dual psn accounts is in the ps3 version of the game. The tweet by David Vonderhaar(sp?) was just reassuring xbox players that their version of the game had the same functionality. There are separate teams for at least the ps3 and xbox versions. This was confirmed by David on twitter. So technically they aren't ports of each others build, and functionality in both versions depends on the team developing that version of the game. I will be getting it on xbox day one, but I may consider getting it on ps3 within a couple weeks of its release