For repotting orchids, it is better to use bark rather than moss. Orchids require a well-draining medium to prevent root rot and promote healthy growth. Bark provides better aeration and allows excess water to drain quickly, preventing waterlogged conditions that can harm the orchid roots. Additionally, orchid bark helps mimic the natural growing environment of orchids in the wild, where they typically grow on trees or rocks rather than in soil. Using moss as a potting medium can lead to overly wet conditions and increase the risk of fungal infections. Therefore, orchids are generally happier and healthier when repotted with bark.