Those are solutions for very different types of deployments.

BDR is asynchronous multi-master, without global transaction management etc.

XL is a distributed database with global transaction management, strong consistency, etc.

Say you have geographically distributed application (managing customers in US, EU, ...). You can deploy a node in each area and direct local users to this node with low latency etc. It also means "no conflicts" (which is a major concern in multi-master), and the changes will asynchronously replicate to the other nodes.

XL would perform poorly in this scenario (at least I believe so), and it's meant more for local deployments, when hitting vertical scalability limits.

No, I didn't try. So I can't compare. I saw the contributors/support from postgres, and I chose BDR.

Well, we're also Postgres-XL contributors, so ... ;-)