A few schools of thoughts concerning left hand vs right hand path.

Left hand path is a devotion to the impersonal self. Self realization, raja yoga, meditation. Any type of direct experience with God. Hinduism and Buddhism falls more in line with this. Some say that following a left hand path is evil or considered dangerous because it uses the practice of magic as well.

Right hand path is considered devotion to personal deity like "God". They seek communion with something other than themself which they personify. The right hand is considered the Abrahamic religions of a masculine God. Bhakta yoga is the act of personal worship of God

Both paths can do either harm or good, depending on the individual's perspective and whatever practices they perform. Thelemites are one example that must incorporate both in their practices.