These articles may help:

• Git vs. Mercurial: Please Relax (Git is MacGyver and Mercurial is James Bond)
• The Differences Between Mercurial and Git

Edit: Comparing Git and Mercurial to celebrities seems to be a trend. Here's one more:

• Git is Wesley Snipes, Mercurial is Denzel Washington

How do you configure it to ignore files?

Ignore is configured in a normal text file called .hgignore in the root of your repository. Add it just like a normal file with:

hg add .hgignore

There are two syntax options available for file matching, glob and regexp. glob is unix-like filename expansion and regexp is regular expressions. You activate each by adding syntax: glob or syntax: regexp on a line by itself. All lines following that will use that syntax, until the next syntax marker. You can have as many syntax markers as you want. The default syntax is regexp, so if you only use regexp you don't need any syntax marker.

You can add comments with #

Example:

# python temporary files
syntax: glob
*.pyc

#editor autosaves
*~

# temporary data
syntax: regexp
temp

Ignore only applies to unmanaged files (i.e. files that are not already checked in). To ignore files that are under version control, you can use the switches -I and -X.