This is what I'm interested in as well. There's a little bit of prior discussion (see links below), but the short of it is that MicroPython is open source while Zerynth is not. For me that makes Zerynth a non-starter, but if that's not an issue for you, they do make claims of a few benefits:

https://community.zerynth.com/discussion/382/zerynth-vs-micr...

https://forum.micropython.org/viewtopic.php?f=2&t=2431

OT: Micropython on an esp8266 is a fun combo. Very easy and cheap to get started.

There's something satisfying about toggling an LED directly from the REPL.

You can also inline assembler:https://docs.micropython.org/en/latest/pyboard/pyboard/tutor...

Agree. I've been using Micropython for almost two years on several projects. This Spamvertising from Zerynth doesn't say why I should switch.