Low resource footprint, written in Go, embed-able in any Go project as a library, compiles to mobile with little to no modification, supports config change without restart, has plugin API.

These were the reasons why we used it in my previous job.

Integrates with Docker Compose with the its Docker config provider so I can configure Traefik for my services through Docker labels, not in the central Traefik instance

HAProxy's documentation is pretty bad (almost entirely of the style "here are all the parameters and options available, no concrete complete examples)".

Traefik has easy to parse docs with lots of examples, and mostly, it can autoconfigure itself based on a variety of sources. You can point it to your Kubernetes or Nomad or Consul, (and with small bits of info given when deploying your workloads to those places), and it just works.

Because Traefik is lightweight and if you know Go, it can be even easier to get going as you can browse the source code and figure things out.

HAproxy on the other hand is the big daddy of proxies. The pinnacle of high performance. There are few use cases where this makes sense. Definitely nothing for development environments.

I use it because it's built in to k3s.

Easy to configure, straightforward and intuitive. Clear and detailed documentation. Recently, I wanted to try HAProxy, but I gave up because I got lost in the config, and I don't trust AI agents to do things I don't understand.

Easy to configure.

We use Kong, and while it is quite powerful, oh boy better get some coffee when doing those rules.