The advantage in AF favors the D300s. I have not seen a quantitative measure to the difference, but the AF system of the D300s is quite good. The D7000 has an updated AF system but my experience is it still falls slightly short.
Take a look at the specs on the D7200 or D400 if they materialize. Otherwise the best alternative would probably be a D600 which does have better ISO performance and a better AF system but you are sacrificing the crop factor (unless you use crop mode). The D600 has some advantages and if you had to make a move based on existing cameras, it is probably the choice.