I think those implying that there wont be a difference in multi-platform games are crazy. With the systems both being easy to develop for this time and having hardware so similar it would be a complete sign of negligence to not have the ps4 version running or looking better.
The PS4 design is just better for graphics, plain and simple.
The Xbox 1 developer on reddit even admitted it yesterday.
"The facts are on paper, the PS4 has better specs and the most you can debate is by how much. What I can tell you is I have played Forza, Killer instinct, and Ryse on the Xbox One. They look as good as the games I play on a high end PC. Ryse reminded me of darksiders II."
For those implying dd3 vs gddr 5 doesnt make a difference here it is in AMD's own words.
http://www.amd.com/us/products/technologies/gddr5/Pages/gddr5.aspx#2
also for real world comparisons. AMD actually released some DDR3 and GDDR5 versions of its own cards
Here are the results of its 2GB DDR3 AMD 7750 vs 1GB GDDR5
http://www.hardware.fr/focus/76/amd-radeon-hd-7750-ddr3-test-cape-verde-etouffe.html
as you can tell the extra bandwidth provided by GDDR5 results in about an average of 30% more frames. Fact is latency is a non-factor in graphics performance, at least in relation to bandwidth.
Add this to the fact, that the PS4 gpu also easily outperforms the xbox 1 gpu, by about another 30-35% on average(and thats with giving a huge benefit to xbox gpu and a slight downgrade to the ps4 gpu in the comparison)
http://www.eurogamer.net/articles/digitalfoundry-radeon-hd-7790-review
BOTH ARE AMD APU's except one has GDDR 5, 18 compute units vs. 12, 32 ROPs vs. 16, really its no contest.
Like Ive said before the PS4 version should always either run at a much higher frame rate/resolution or just plain look better if the developer chooses to lock both titles at a set framerate. And for those implying that developers will just go for the lowest common denominator, and make them the same, well theyre just ignoring all video game past. Fact is games dont exist in a bubble. Games have to compete with other games as well as first party. All it takes is that first one game to push the ps4 hardware and all it's competitors have to follow suite or else be left in the dust.
Now Im not implying the XB1 is another Wii U. That's far from the case. All im saying is that while both will be a major leap visually over what we have on the console market at the moment, the PS4 will go just a bit further visually, due to being close to 50% more powerful graphically.
Yet of course, it still all comes down to which system's library/culture interest you the most.