Gran Turismo 6 feels a lot like the Gran Turismo 5, but Polyphony has made a lot of cosmetic updates and engine improvements. The new homescreen is cleaner and faster to navigate. All of the dealership are updated with the new models from automakers (still no Porsche though, damn EA contract). GT6 doesn’t differentiate between so-called Standard and Premium cars like GT5 does. This is good news if your favorite car is one of GT6’s older, more obscure models.
When it comes to tracks, GT6 comprehensively murders absolutely everything else out there. It is, hands down, the best range of circuits assembled for a racing videogame I’ve ever played. Forza can't offer that - Forza 5 doesn't even have Nürburgring! However, one thing that Forza does better (and my only complaint with Gran Turismo) is sound! The exhaust pipe and tire screeching still feel a little flat in this game. This can be overlooked if you have a nice sound system (subwoofers add depth and richness).
Overall, it is a fantastic update that is impossibly good looking for a PlayStation 3 game. If Polyphony addresses some of the gripes that are still haunting the series, it would be excellent.