I will not say why this plugin may be better as I'm naturally biased, but you can check the features from both plugins (mine under https://graphql-api.com/features/) and see how they compare.

I haven't tried, but I believe that you can actually install both plugins side by side (using WPGraphQL's single endpoint, and my plugin's Custom Endpoint under a different route), and using the same GraphQL queries to test them, check their speed, usability, security mechanisms, configuration, extensibility, and anything else that could be relevant for your project.