Final answer:
The main difference between Vincent and Anton stems from Vincent's natural, unenhanced genetics, which intensify their rivalry in a society that prizes genetic perfection. Vincent's efforts to outdo Anton's genetic advantages underscore the broader themes of the film about human will versus genetic determinism.
Step-by-step explanation:
The main difference and cause of competition between Vincent and his brother Anton is based on their physical and genetic capabilities. In the context of the sci-fi film Gattaca, Vincent is a "faith-born" child, conceived without genetic selection, which makes him genetically inferior to his genetically engineered brother, Anton. This inherent difference fuels a rivalry, where Vincent strives to prove his worth and capabilities despite not having the genetic enhancements that Anton has.
The competition between the two is further exacerbated by the societal values depicted in the film's universe, which favor genetic perfection. Vincent's tenacity and determination to overcome his genetic shortcomings drive the narrative and highlight the significance of personal willpower against predetermined genetic destiny. As the crux of the plot, this rivalry and competition bring to light issues about the ethics and implications of eugenics and the definition of humanity.