Yes i know this topic is over a year old, but it's something i've been experimenting with over the past couple of days.
The GTRE and PS2 GT4 versions are virtually identical and due to the publicity they've both received, one must deduce that they're accurate, their similarity would support this.
The closest GTR2 version to these is NOS2008 v1.0 by "someone who got banned".
I was dissatisfied with both Raceking and Dutchdevil versions, i can't remember exactly why but i didn't keep either of them. I recall one of them was too narrow and the other got most of the corners wrong.
NOS2007 v2.03 and NOS2007 v2.21 are basically the same track and both have the same arguable errors in the first sector where the road rises/falls in new places, with a few corner profiles being different.
v2.03 comes with a fog mode and a couple of other things which i didn't bother trying.
I noticed a drop in framerate when playing v2.21, though there is a lot more visual detail present.
For me it comes down to a straight fight between NOS2007 v2.21 and NOS2008.
08 is lacking in a couple of areas being that the AI drivers do brake in some odd areas and the lines they take are not optimal in a few areas - most notably at the Carousel where they hook two wheels over the inside kerb (very occassionally resulting in overturning).
2.21 has some peculiar nuances that result in the player being forced to go through corners far slower than on other versions, and slower than the AI. Often you're caught between being rear-ended or understeering off the track as if you've suddenly hit black ice.
My choice is NOS2008. The experience of driving it is superior and more consistant than other versions, i'd rather there be an issue for the other cars than there be an issue for me.
If someone were to fix the AI, lighting issues, occasional flickering and scenery popups then it would be a perfect conversion.