When comparing pygame vs Defold, the Slant community recommends pygame for most people. In the question“What are the best 2D game engines?” pygame is ranked 9th while Defold is ranked 31st. 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 Easy to learn
Defold uses Lua, which is regarded as an easy to learn language by most.
Pro Completely free of charge
Software and online dashboard are free of charge.
Pro Good combination of visual editing + code (Lua)
You can do a lot with drag and drop, but you're not limited -- the code (Lua, which is easy to learn) allows you more power than just visual editing usually gives you.
Pro Visual editor
Pro Easy and fast export for various platforms
Pro Fast results
Going from idea to result is very important for the creative process.
Pro Very performant
Being crossplatform it is important to work on low end devices.
Pro Collaborative
You can invite friends from the dashboard and create games together.
Pro Great community
A very active and friendly community in forums.
Pro Hot reload
It allows you to change scripts in a game while it is running live. Common use-cases is to tweak gameplay parameters or to perform debugging on a running game.
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Con Outdated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 Google account needed
You need a Google account to develop with Defold.