The biggest difference between Mercurial vs. Git is the branching structure. It can be argued that branching is better in Git than in Mercurial. Even though Mercurial may be easier to learn and use, its branching model often creates confusion.
Is Mercurial better than Git?
While it has its limitations, using Mercurial is way easier than Git, and users of Subversion will find it easy to transition over to Mercurial. This tool also has better documentation, so should you have any issues using Mercurial, you're sure to find an answer to your question soon.
Can you use Mercurial with github?
The answer is: yes, it can! You will be able to do that by using the Mercurial bookmark, which are the Mercurial counterpart of Git branches and are used as such by the hggit plugin.