Comparing JACK and PulseAudio is like comparing apples and oranges. And honestly, JACK by itself is unsuitable as an audio server for general desktop usage.

JACK doesn’t support device hotplug (ya know, connecting and disconnecting a headset, something most of us do) and it also doesn’t support multiple applications generating audio without the user having to configure how audio is mixed.

JACK is designed for low latency in environments like Digital Audio Workstations (DAW) where you know 1) what audio hardware is present at all times, and 2) what applications are going to generate audio.

Many people who use/used JACK ran a PulseAudio bridge on top of it for every application that wasn’t the one or two applications that needed ultra low latency audio.

PulseAudio had some major warts, but JACK wasn’t some panacea that did everything better.