If you look at the pictures posted by Chromatic in the PCARS thread, pictures in the rain are hyper realistic, way beyond GT5's level,but you are right PD seem to suck every last ounce of performance out of a console.
I have seen them and stuff like the rain drops look much better but that is expected given the extra power or lower frame rate it will be running on consoles like PS3.
I think though from current knowledge about next-gen consoles, a GT game on PS4 will be graphics king by far for many years until developers take full advantage of top end PC GPUs.
As the uploader states that's mainly because the videos are shrunk down into very small size, when you do that with any game it starts looking better. But run GT5 and pCARS at full screen and it's clear which is better. Plus weather effects are far from finished on pCARS.
I really don't know how you expect a PS4 game to look better than pCARS on a top end gaming rig. As good, maybe, but better? I don't see how.
I have run both on full screen, 1080p. You can see where pCARS is better due to hardware power or target frame rate but visually you can see the higher quality assets of GT5.
PS4 will have something a bit better than 7850. 7850 can play pCARS maxed out visually at 1080p AFAIK, depending on how much post-processing you do so can vary from 30-60FPS. Sure if you have say two GTX 690 in SLI you will have higher frame rates or resolution but the graphical quality will remain the same. The game will most likely be more optimized soon so even on a 7850, you will start getting higher frame rates than you currently do.
The reason why I say better is, PD will have a bigger budget, will most likely have a more efficient graphics engine as well as much higher quality assets with strive for photorealism throughout game.
If you download say this 458 video, which will probably be "pre-alpha", you can see what GT engine designed for PS3 could do:
http://eu.gran-turismo.com/gb/gallery/d10555.html
Now imagine what they could do with something that is as powerful as PS4, a game designed to take advantage of visuals for target system from the ground up. PD have always had to make games highly limited due to consoles and frame rates they aimed for but PS4 represents finally where they are on a equal footing and can show their graphical skills off.
WOW. GT5 looks and sounds MUCH better.
Project cars is going to fall off the radar imo.
Car sounds in GT5 are quite poor in general so I think pCARS will sound quite a bit better in general.
pCARS is unlikely to fall of radar, it so far looks to be coming a long well and given there are not many games like this on consoles, I think it should do OK.
Concern will be competition around release and also console versions frame rate and graphics look in-game might hit reviews compared to PC version but physics seem good so far so should do well.