It really depends on the driver, car and track. AWD will always have an advantage on off the line starts but once you get going a good FR or MR in the right enrvironment actually has an advantage over AWD.
FR and MR will make the car more pointy and nimble on its feet when it comes to direction changes and cornening, not to mention the huge weigth saving benefit of not having any awd components, rembember they add weight and mess with how quick the can point its chassis to your will.
If you are not running out of grip as long as the track and setup isn't putting you at a disadvantage you are better of on the the FR or MR if you know how to handle them. There is a reason formula 1 nascar Le man cars etc are all running RWD setups and on the other end cars like WRC runs AWD. Its not as simple as which drivetrain is superioir, it depends on othe other factors.
That said I personally have a huge bias toward AWD especially when it comes to production cars cars and beleive its superioir to the others, even with the things i Just mentioned. Many times it can goes to waste but if on the right car and setup AWD is something I enjoy a lot more than the other drive trains.
BTW I have no idea what you meant in your OP. WHether the PP for AWD cars should be higher ib gt5 becaue they are too fast, or if in real life they are faster but in gt5 they are not because you have seen their PPs are not bigger than FR or MR etc.