When comparing CheckiO vs Google's Python Class, the Slant community recommends Google's Python Class for most people. In the question“What are the best resources to learn Python?” Google's Python Class is ranked 2nd while CheckiO is ranked 18th. The most important reason people chose Google's Python Class is:
This is a free class for people with a little bit of programming experience who want to learn Python.
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 Great for people with little programming experience
This is a free class for people with a little bit of programming experience who want to learn Python.
Pro Good mix of theoretical and practical material
The class includes written materials, lecture videos, and lots of code exercises to practice Python coding. These materials are used within Google to introduce Python to people who have just a little programming experience.
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 Some programming experience is required
While the courses cover the very basics of Python, basic understanding of programming is needed to start learning from Google's Python class.
