For me the only bad things in the graphics of GT6 are:
-The shadows: related to a low LOD (Level Of Detail) distance outside (you have less detailed and flickering shadows) and inside the cars there are no shadows generated by the little parts (Pagani Huayra is the best example of how plain looks without them), though at least we don´t have blocky shadows inside the cars...now we have huge black dots/marks over the track.
-The darkness while in cockpit view: tracks looks way too dark at some points of the day, if you change to "hood view" you can see the massive difference (is like using sunglasses). HDR related, better lighting reflected and reacting with the car from outside, low effects inside of the car.
-The poor anti-aliasing mixed with the HDR creating a "blurry effect" at the distance. Tracks with less populated details as Willow Springs in where you don´t need to use too much anti-aliasing and such looks beautiful though. Less objects, less post processing to add.
The game looks below 60FPS in cockpit view but still quite fluid, once outside the car it looks a little bit more fluid. Frame rates are not consistent yet nothing that disturbs me at least as happened with GT Academy...to me it was unplayable with those frame drops at Silverstone with one car.
There is motion blur in replays but the game has more anti-aliasing and details, yet running at 30FPS as in GT5.
Compared to GT5:
-The Shadows were overall better and consistent in the whole environment (car included), but it was like having them in low settings with more LOD distance. It gave Nürburgring a better look because of how the light passed through the leaves. They looked more like actual shadows and not like massive black spots appearing at the distance.
-Cockpit view also looked more clear and natural.
-Anti-aliasing was almost the same, but the cars even while looking good if you used the rear camera you could see some dents...
In GT6 we have adaptative tessellation and it is noticeable when you are at about 20 meters from one car and you can see that it doesn´t look as sharp or "finished" as when you are really close to it. (that´s how it works...more close the more polygons/details you have, the far the low polygon count is and less detailed the car).
Having in mind how realistic the cars look and lighting in photo-mode...GT6 is the better looking game. Having in mind how good Apricot Hill and Willow Springs look, all those minor details in the environment...GT6 also takes the cake.
Rain effects in the windshield look good or clear in GT6 and not pixelated as in GT5, yet it was more realistic in GT5.
Textures, if you could test most of the cars in GT5, you may notice a lot of improvements in the interiors of a lot of Premium cars not just the standard ones. The Miura, also the old Jaguar XJ something (can´t remember right now, the old green one with the V12...lol) looks way better when it comes to texturing in the cockpit, the wheel of the jaguar looked blurry in GT5 and now it actually looks like made of wood, and the Miura details are more defined. (they also fixed how the lights goes up while turning them on)
Imagine this game looking like in the trailers...well that is actually how GT6 should and could look in a PC with all graphics maxed. But instead it is running in an 7 year old console with just 256GB of RAM...nowadays a regular gaming PC uses 8GB of RAM, and GPU´s (graphics cards) uses from 2 to 4, and the most expensive 6GB of vRAM for graphics.
Imagine what PD can do with 8GB (but for real usable are 6GB) in the PS4 if they managed to make GT6 almost photorealistic in photomode and even while playing as happens in Willow Springs...
Just imagine that...this game needs native 1080p, MSAA X4 or X8, shadows and textures at higher settings...and done. 256GB of RAM...I have 4GB on my PC and is as old as the PS3, my GPU has 1GB and for games at native 1080p is enough but for games with really High quality textures I´m in the need of one extra GB already.
The truth is that PD tried to do way too much stuff at once in a weak piece of hardware.
Sorry for TL DR.