You have a point - I don't shoot sports regularly, only BIF. At first I thought the D7100 AF was erratic, but that was probably operator error - over time I got a consistently high keeper rate with it... I shot hummingbirds a few times with it and was blown away by how many shots were tack sharp! Overall, I rate the D7100 on par with the D800 - which is not bad company at all since the D800 is much more expensive and has a lower pixel density.I bought a used D300 because the D7100 was so bad for sports, maybe i had a bad one who knows, but it was only for sports, it was fine for wildlife
i thought the d300s was exactly the same as the D300
That last point may be affecting your perception, too - the D7100 is a lot less forgiving when it comes to AF precision than the D300 with half the pixel density!