If the rumors are true, what'll be the graphical difference between 720 & PS4?

[Zappykins]

Both are going to be very good looking.  The difference will be significantly less than the difference between DirectX 10 and 11 in this demo (sorry for the bad music): http://www.youtube.com/watch?v=YiS6kzXQch

You have to get more than a 50% difference to make it visually noticeable (think PS2 to Xbox.) So with the current stats that have the NextBox about 30% less than the PS4 it wouldn't really be all that noticeable. I would think it would be a little more than the 360/PS3 differences.

Assuming the Xbox is less powerful, it could be even less as DirectX (Xbox) has become arguably powerful than OpenGL (PS4/WiiU) since DirectX 9. Look at how good Halo 4 looked, and remember it's hardware was mostly designed in 2004. Microsoft has refined DirectX 11.x with the next gen hardware in mind AND there will not be a new DirectX 12 until Windows 9 – so the NextBox/PC games will be even more similar.

Now, I would not be surprised if the hardware is a bit more powerful than the rumors. PS4 is still only 70% of what Tim Sweeney wanted. So if MS kicks up the next box GPU to the 2.5 Tflops he wants, it would mostly be bragging rights, probably not dramatically noticeable.