Deno has members in Ecma TC39, so they take part in the development and standardization of JS.
Deno brings a new mentality to development focused on simplifying things, whereas Bun aims to be an improved Node.
Deno aligns with web APIs: you can use the same APIs in the browser and in Deno. Many packages work in both platforms. Deno is even in the compatibility tables in MDN.
Deno simplifies DX greatly. It's very easy to work with Deno. Easy to install things and set up a project, easy to deploy, no config files etc.
Deno is written in Rust, which allows them to move faster and more safely. Contributing to and extending Deno is a breeze. You can add Rust crates to the runtime and use them from JS.
I feel like the Bun team has been too pressured by executives and marketing. They announced 1.0 when Bun was clearly not stable enough, giving lots of segfaults. Even their readme had a huge statement right in the beginning saying that Bun was not production ready yet, despite 1.0 being hyped all over the place.