For the side by side comparison, we are comparing Takata Dome #18 liveries of the QuatrroX Takara NSX to the NINCO NSX.
In the photo below, the NINCO is on the left with the darker wheels, the Takara with the bright green wheels.

The NINCO is still on the left and the Takara on the right.
You can see the difference in front and rear profiles.  You also get a little peek at the white sidewinder gear underneath the Takara.  I know some of this gets into asthetics and what some people like versus what others like, but I think the darker plastic of the rear lens area of the Takara looks more realistic than the brighter of the NINCO.  The rear bumper of the Takara looks a little high, but I can get over that.  Now we need to check out the sides of the cars.
Once again, NINCO on the left, Takara on the right.

Can you make out some of the differences?
Takara front wheels are larger diameter.  The front tires of each are about the same width however.  The rear tires of the NINCO are about 1 or 2 mm wider (sorry, didn't measure it).
The air scoop of the Takara sits a little further back and higher, not to mention the Takara has a soft, flexible antenna.

Now for the chassis.

The NINCO on the left, Takara on the right.  Noticeable differences are the anglewinder vs the sidewinder, gears on opposite sides of the rear axle.  Braids...(this is as they came out of the box): NINCO braids are long, smooth and straight.  The braids on the Takara look like they have been beaten up on the bottom side of a black windowed, Audi TT basher kids car.  while it didnt impair the performance, you would hope that the braids on a new car didn't look like they had already had a hard race life.
This is also the first glimpse of the Takara "plug-n-play" digital module area (more on that later).  Magnets are the standard button in the NINCO and bar in the Scalextric/Takara.  You can kind of make out the width difference in the rear tires here.

Thats about it for the preliminary side by side.  Now its time to take the body off to see what's "Under the Hood".