That's not usually a choice. nginx is first and foremost a web service and a proxy. It is not built primarily for rewriting traffic and simple run time state changes, which is what you generally need an http router for
Normally you choose between something like Apache and nginx, where nginx is a bit easier to configure and write modules for, but the former has more functionality and third party support.
You choose between haproxy and something like Varnish, where the former is a bit more featureful on the routing part and the latter has more focus on the caching part.
Normally you choose between something like Apache and nginx, where nginx is a bit easier to configure and write modules for, but the former has more functionality and third party support.
You choose between haproxy and something like Varnish, where the former is a bit more featureful on the routing part and the latter has more focus on the caching part.
It is not uncommon to use both.