Not much has been released about the Xbox720. The PS4 released a good bit of information in an article the other day though. So far we know that they have scrapped the Cell Processor for an AMD which makes their games not compatible with the prior games. This includes PSN games. You will have to start completely over with PS4. I'll repeat that again to show the gravity of that, PS4 is not backwards compatible to ANY of the prior systems including games you downloaded from the Playstation Network. They included a share button on the controller that links directly to your facebook. And a few other changes.
You can find a ton of news on the PS4 on GameInformer.com.
As far as which system is "better" that's not decided yet. Won't know until more info is released on Xbox720. And even then you're going to have people who will fight for their system.