It definitely depends on your use case, so it's hard to tell what's better for you. HAProxy is solid and doesn't take a long time to get started.

At the same time, some of the HAProxy 2.0 features have already been available in Envoy and tested in production, at scale (if HAProxy provided those features, there wouldn't be a big need for Envoy). For example, Envoy is pretty extensible, has good performance and has good support for dynamic cert management (including service-to-service mutual TLS).

Envoy was built for that purpose and has more functionality around it, as well as better support for service discovery (developing the now open standard APIs), more protocol introspection and observability, full-duplex connections (no upstream/downstream split in what's possible), and easy interchange between protocols.

Envoy is also used by Istio and has a lot of infrastructure support for deploying in Kubernetes and such which HAProxy doesn't currently have.