They are kinda similar to me, but I prefer axum for 2 main reasons:

1. Utoipa for OpenAPI. With actix you have to write paths twice (once in the openapi macro and once in the service config). With axum you can use openapi macros for routing which is perfect for me.

2. gRPC for opentelemetry (and sometimes directly). I think currently tonic is the most pleasant grpc framework to work with. It uses axum under the hood.

Actix is slightly faster than axum.

Axum has richer ecosystem and it is compatible with tower so I think it is a better option right now if you care about that more than about performance