To me, both Polyphony and Simbin approach their FFB design quite differently. In Race 07, the FFB are stronger and gives out a lot of info (engine rumble, bumps in the road) although at times it can feel a bit canned. Still, you do get a great sense of immersion which makes racing more engaging. In Prologue, the FFB are not as strong (I have my G25 set to max in the game) and you don't feel the road as much. But it does feel a bit more organic- by that I mean it feels as if each of the FFB components are seamlessly connected to the next. The effect is that you can sense the difference between the cars more clearly.
Again, the same applies to physics. Those who aren't used to GT physics might find it problematic in certain areas. One of them being tire grip. Unlike racing sim which is based around GT or open wheel race cars with racing slick and stiff suspension, most of the cars in GT are road/production cars with either "S"(Sports) or "N"(Road) tires and softer and pliable suspension. With softer suspension and the heavier weight of production cars, you have to deal with weight shift/transfer between the tires that usually the cause for loss of traction during cornering (sometimes more than the tires themselves). That's why in GT5P, you would even lose traction even at low speed cornering- if you're turning right, and weight of the car shifts mostly to the outside (left side) and you apply too much gas, the car would then spin. It's less common in racing sims like Race 07 because the suspension is much stiffer and the cars are usually lighter.