Which sentence is more formal?

 - Wikipedia offers articles in close to three hundred languages, including Zulu, Cherokee, and Samoan.
 - Wikipedia has articles in a bunch of languages, including Zulu, Cherokee, and Samoan.
The first sentence is less formal. You can tell because it uses overly simple or imprecise language (has, a bunch of).
The second sentence uses more precise language, so it is more formal overall.