Science H provides a wonderful overview of the entire range of scientific inquiry and a superb introduction to the world of science you will explore in years to come.
If you've done a lot of Sonlight science in the past, you may sense Science H covers much of the same ground you have covered previously. That's correct. But the Science H approach is fresh and intriguing and introduces a significant quantity of new material. Assuming you have already used four or five years' worth of Sonlight science, however, feel free to use Physical Science 150-00. There are plenty of additional courses to come!