JACK seems like a much better low latency solution to me but it's a
bit more work to use and it isn't installed by default with most Linux
distributions. PulseAudio is used by Gnome and several mobile handsets
so it is more popular by default. Popularity isn't really important
but problem free audio usage is.
PulseAudio has a legacy compatibility layer and I haven't had any
reports of problems from baudline users. I recommend in the baudline
FAQ to disable sound daemons because they tend to create all sorts of
audio problems. So are people disabling PulseAudio or is the
compatibility layer working fine with baudline?