Those are both good strains. The Lactobacillus GG is the same as Lactobacillus rhamnosus in Flora Prime. The "GG" designates a specific strain of lactobacillus rhamnosus. The S. Boulardii is a yeast organism that grows at best at 37 degrees, and due to the variability of temperatures in the digestive tract, I chose not to use it at this point.