When comparing CheckiO vs Code Avengers, the Slant community recommends CheckiO for most people. In the question“What are the best resources to learn Python?” CheckiO is ranked 18th while Code Avengers is ranked 25th. The most important reason people chose CheckiO is:
Users can publish their solutions for different problems and other users can review the code and give their opinions on how they would have solved the problem. Sometimes, some of the most active users get their code reviewed by Guido Van Rossum (the creator of the Python language) himself.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Community backed solution reviews
Users can publish their solutions for different problems and other users can review the code and give their opinions on how they would have solved the problem.
Sometimes, some of the most active users get their code reviewed by Guido Van Rossum (the creator of the Python language) himself.
Pro Available in multiple languages
CheckiO crowdsources translations for problems. Currently problems have been translated in 10 languages. So it's highly possible that eventually more languages will be supported.

Pro Ability to create new challenges
New missions can be created and uploaded using GitHub. After that is done, it's suggested to CheckiO and if it fills all the requirements after being reviewed by a CheckiO team member, it's pulled into the game.

Pro Challenges from GitHub, O'Reilly, Dropbox and Hubspot.
Pro Reinforces concepts through fun interactions
Code Avengers makes their material engaging and interactive, which aids with understanding and retention of the material.
Pro Full of context
Explains what everything is before you must use it, unlike Codecademy, which just kind of tells you to do stuff. To figure out what everything is exactly, you must either look at the glossary or google it.
Pro Wide selection of courses
Not only do they offer Python, CSS and HTML, and all the works, they offer them in context packages, where you can work on a project that utilizes one or the other. Also, there are different recommended tracks for different purposes - web designer, etc.
Cons
Con Not for absolute beginners
CheckiO does not teach syntax, instead it teaches how to solve problems using a particular programming language therefore some basic programming knowledge is required to start.
Con A little slow
It may be slow, but that's only because it's thorough.
Con Limited selection of courses
Compared to many other paid learning resources, Code avengers currently has a limited number of courses to choose from.
