The good folks at Digital Foundry have posted a direct comparison of Dark Souls 2, comparing the game's PlayStation 3 and PlayStation 4 versions on video.
All footage of the game was taken from its Gold Master version, which is the final version (perhaps sans a day-one patch) that is currently available only to the press and to the publishers themselves.
For those not in the know, a Gold Master is the version of the game that's sent out to disc manufacturers, which in the digital age would be Sony, who are releasing the game on their online store platform.
In any case, you can check out an in-depth article about the differences between the two versions of the game here.