I would like to host my code in the cloud. Which one would you recommend?
Neither GitHub nor Bitbucket are SCMs -- they are just hosting services built around Git and Mercurial, which are the underlying SCMs. If your question is actually whether you should use Git/Mercurial as an SCM, then most people will answer "yes", but it sounds like you should read up on exactly what these are before diving in, since it sounds like you have quite a bit of confusion on the topic.