...or you could just open the file directly in Illustrator and use it's superior vector tools. If you open (rather than place) a raster image, you will have a full resolution file to work with, just like Photoshop, but it cuts out a few steps.
Manually drawing paths, whatever way you want to do it, is by far the most accurate. I like Streamline over Sillouette (although not by much), but I don't really use either of them regularly. By the time you've fine-tuned all the settings and manually corrected all the paths, you may as well have done it all from scratch.
One exception, though, is more expressive illustrations where accuracy isn't so important. Try using Streamline on a photograph for example, it's pretty effective!