AppRunner is super easy to deploy app, infra including log base, monitoring base.
Its monitoring base enable to watch enough metrics.
Built infra is decoupled from the other services.(it will need to open peering conection to other VPC if you want it to connect to db and so on)
AppRunner can deploy code from console editor like AWS Lambda or GitHub repogitory somoothly, And also can deploy container app via AWS ECR. but it does not have sidecar container concept. so if you want to use DB or cache server, you need to open VPC peering connect.
If you want to release simple lightweight app, AppRunner is smart option rather than AWS Lambda or AWS Fargate.
But it needs to use RDS or Aurora if you want to use DB, it will be more expensive rather than EC2 for small start.