>>76521502
Chinups rotate the humerus in such a way that if you do full stretch the lats really work through a fuller ROM, which leads to better development. Also, bicep activation is more complete in chinups. Basically, chinups fully engage more mucle in the contraction, which means one can be stronger. This is good.
Pullups, however, arent trash. Its just that the limiting factor in pullups can be forearm and that tiny brachioradialis muscle failure. If your relatively smaller/weaker forearm and/or brachioradilais muscle fails, you fail and your back stop getting worked. This means that ultimately, you can also do more volume with chins than pullups, which is good for back hypertrophy.
Ideally, one cycles and periodizes traing to develop proficiency in both movements (work in neutral/hammer grip, also), as the one poster is correct that pullups have a greater functionality, or at least real world use - jumping over a tall fence requires a pull-up like motion, not a chinup like motion.
But for strength and bodybuilding, chin-ups are better.