They synergize each other.

BPC 157:
BPC 157, a derivative of body protection compound (BPC), has a dose-dependent effect on the growth and migration of fibroblasts, the cells responsible for extracellular matrix repair8. It has been shown to accelerate the healing of many different wounds, including transected rat Achilles tendon2. BPC 157 significantly accelerates the outgrowth of tendon explants, increases the survival of cells under stress, and markedly increases the in vitro migration of tendon fibroblasts2. It also enhances the growth hormone receptor expression in tendon fibroblasts6. In terms of muscle healing, BPC 157 induces healing of mechanically severed muscles due to complete transection, crush, and denervation injuries9.

TB 500:
TB 500, a derivative of thymosin beta-4 (Tβ-4), produces a similar effect to BPC 157 by manipulating actin, a protein that plays central roles in cell reproduction and migration8. TB 500 has been shown to be effective in treating common sports injuries along with skin burns and wounds1.

Comparison:
When it comes to tendon, ligament, and bone injuries, both peptides have been extensively tested and have been shown to have dramatic benefits8. BPC 157 has been shown to accelerate growth of tendons by increasing fibroblast growth, survival, and migration8. Studies of healing tendon show increased levels of bFGF, EFG, and VEGF following the administration of BPC 1578. Conversely, TB 500 helps spur muscle growth1.

https://www.reddit.com/r/PeptideGuide/comments/192d8m5/bpc_157_vs_tb_500...