Both have their own risk and fortune. A natural deep conditioner will take a longer time to show results, however, it will deeply care for and nourish your head (scalp, hair root, and hair). Meanwhile, synthetical deep conditioners likely show instant results in less than three uses, but they may irritate your scalp.
They also have different scents and textures. So, each category has its own pro and cons. Nevertheless, if your hair needs instant rescue perhaps the chemical contains ingredients that would be good to try, too.