In the PS4 version of God of War 3, the development team will be increasing the resolution from 720p to 1080p. A smooth 60 frames per second is also being targeted (the original version had a variable one that jumped anywhere from 30 to 60 frames).
Along with a digital release, God of War 3 Remastered is also coming out on disc. If you are interested, you can preorder the physical version with this link on Amazon. The PS4 version is coming out on July 14th.
The PlayStation 4 came with a 500 GB hard drive while Sony also recently announced (and released in some parts of the world) a 1 TB model. While the PS4 currently does not support external HDDs, gamers can easily replace the default hard drive with a compatible alternative such as the 2 TB Samsung Seagate HN-M201RAD, which you can check out with this page.