The D300s has the same image processor as the D90. I have a D90 and a D7000. The D7000 is at least 1.5 stops better than the D90 at high ISO. My D7000 with the AFS 50 f1.8G at ISO 4000 is at least as clean as the D90 at ISO 1600. And, with 16MP vs 12MP, that difference is magnified when cropping. I would be shocked if the D7000 did not similarly beat the D300s.
That said, the D300s has the 51 point pro AF system, while the D7000 has the newer, but slower focusing 39 point system. The D300s wins here hands down, and that difference in lock-on speed is a real practical advantage in shooting basketball. Also, the D300s can be had with the grip to increase FPS to 8 (vs 6 FPS max for the D7000). To me, this is not a practical advantage, as 6 FPS is enough for basketball.
Despite the AF and FPS advantage, I would not trade my D7000 for a D300s, since the D300s is really not clean enough above ISO 1600 for my taste in shooting hoops - and ISO 1600 is not fast enough for most indoor gymnasiums with available light, even at f2. So, I do consider the D7000 to be a significant upgrade in high ISO performance from the D300s.