Its definitely not far superior to PD, it might have more polygons and more resolution in forza 5 because its next gen, but still the cars really dont look better, they dont look that real-life like, they look like being a game, GT cars manage to feel and look more photorealistic..., and obviously its cheaper thats why they outsource, the outsourcing country salaries are far less expensive than american ones, its like companies that have the factories in china because their labour force is much cheaper.
And a game that when you take a corner says "good corner" and when you overtake says "good overtake".... well, it is laughable really, not to talk about the behavior of the cars, weird to say the least.