A 'beginner's' impression, which may be helpful if you are also beginning:
PIAF is great, but as echoed in the
NV article, overly complicated, and overly dependent on 'complicated' components - it is fairly trivial to configure.
Asterisk-Gui promises simplicity, as in simple to run, simple to port or restore - if only it were simple to configure...
As with any project, and PBXes seem like ground-hog day to me (I'm always a beginner, because the previous system worked so well for so long!):
First, I choose the best technical implementation based on recommendations from the web (and then disregard, based on cost)
Second, I choose the best FREE solution (and then also disregard because of lack of clear, comprehensive instructions )
Finally, I choose the solution that provides full WORKING instructions for my scenario!
Luckily, from my perspective, PIAF is number 1, 2 & 3 in this respect!
The new Asterisk-Gui may well become No.1, but until more guides/examples appear (and they will), it may not be suitable for everyone.