IGF-1 LR3 is a modified form of insulin-like growth factor with extended half-life that directly stimulates muscle growth, while CJC-1295 works by increasing natural GH/IGF-1 production.
Research summaries indicate both can enhance muscle growth, but CJC-1295 is generally considered safer as it works through natural pathways. IGF-1 LR3 requires more careful management of blood sugar and has greater potential for adverse effects.