There is no one definitive answer to this question since everyone's individual needs and preferences will differ. However, some possible contenders for the best GF line might include: Garden of Life RAW Probiotics Ultimate Care Renew Life Ultimate Flora Critical Care 50 Billion Vitacost Probiotic 15-strain Formula Each of these options provides a broad range of beneficial probiotic strains at a relatively high potency, making them ideal for those seeking comprehensive gut support. Ultimately, it comes down to personal preference as to which line is the best for you. Whichever option you choose, make sure to look for products that are third-party certified to ensure quality and potency.