(almost) All L2s are essentially the same - so what matters is "CC" - Community and Connections (i.e. integrations you offer to builders and users alike).

Who has them ... here's your answer from Token Terminal 🤓

Base makes it easier for developers to build apps by offering seamless integration with Coinbase’s products, users, and tools. Access to 110 million verified users and over $100 billion in assets is kinda hard to beat advantage over building on other Layer-2s 😉
(apart from getting their airdrop money, ofc)

Base's integration with Coinbase gives developers access to a huge community and assets, making it a top choice for app development on Layer-2. Community and connections are key in the crypto space, and Base seems to have a strong advantage in this aspect.