When comparing pygame vs Nez, the Slant community recommends pygame for most people. In the question“What are the best 2D game engines?” pygame is ranked 9th while Nez is ranked 76th. The most important reason people chose pygame is:
Pygame uses Python as its scripting language. Python is widely considered one of the easiest languages to grasp even for beginners.
Specs
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Pros

Pro Easy Python syntax
Pygame uses Python as its scripting language. Python is widely considered one of the easiest languages to grasp even for beginners.
Pro Very easy to understand
The API is very straightforward.
Pro Good canvas system
Pygame has a drawing system that allows the user to create and draw on an unlimited number of canvases.
Pro Active community
The community is very active, so if you ask for help you'll get it relatively quickly.
Pro Open source
Completely free, no need to pay for licenses.
Pro Cross-platform development thanks to the use of mono and xamarin
Nez is built on top of monoGame and can be used the make games for many platforms (Windows, Linux, Mac, Android or IOS).
Cons
Con Very basic
Pretty much just a wrapper for SDL.
Con Messy documentation
The docs are messy, and some basic functions are infuriating to work out. There's even some places in the documentation where it's clearly wrong about how a method is called/what the arguments really do.

Con Deathly slow
Con Outdated
Pygame uses a really old version of SDL and is missing some of the features developed for SDL2.
Con Nonexistent community
No good forums, wiki, or other ways to reach other Pygame developers.
Con Hasn't been updated in years
Con Pygame is a language, not a game engine
Physics, AI, networking, and input are not supported.
Con Just a framework
Meaning there's no visual scene designer so you'll have to write your own.