The D300s is known to be the same camera like the D300 if you would check out the features. There are just some slight differences that will make it obvious that the D300s is considered to be an upgrade of the D300. The D300s will have the ability to shoot in HD but at 720p resolution.
Another thing that you will notice is that the sound will also be different. The 24 FPS with stereo audio is another feature that the D300s has to offer. When it comes to shooting, D300s is also faster than the D300. There are also 7 FPS modes that are available for the D300s.