What Site to Purchase Passes from SBB/ Euro Rail

Hi again - confused on what site to purchase the Swiss Pass?? When I went on the SBB site it gave me a better rate for our family compared to the Euro Rail Site. We are a family of four - My son is 19 - (Youth Pass) 2 Adults and my daughter is 15. They said on the SBB site that since she is 15 she doesn't need a ticke when traveling with an adult to include a family pass card??? Before I purchase and where I purchase the passes from is conflicting and confusing and with the cost I just want to make sure I am on a secure site. The Euro Rail site doesn't offer a 15 Day Youth Swiss Pass compared to the SBB Site. Where it the best place to purchase the Swiss Pass from??? SBB , Euro Rail - My Switzerland???

Just purchased my ticket from the SBB - Swiss Rail site - ( It was a little bit more money) but I felt I that if I purchased from the Swiss Rail and if there was an issue when we were traveling in Switzerland with our tickets we would have better communication with the SBB then if we bought them elsewhere. Again - thank you for all your help!!