XP is easier, and that's why there are more people using windows than linux. You just stick your XP CD in and watch the magic happen. And that's generally all you end up doing: watching while XP takes control for you.
In general, Linux is much harder for a beginner to setup and get everything working properly. It's not so much that it is actually more difficult, it's that windows has inudated the computer industry for so long that many people don't know any other way.
In the end, Linux offers more power and control, but at the cost of effort. There is so much to learn about Linux because there is so much to do with it. There are many guides and lots of general information available at the
Linux Documentation Project. If you learn everything that's available there, you'll be the veritable linux guru.
For fast and quick reference on specific commands, Linux is a step above Windows. The 'man' (short for 'manual') command is a Linux user's best friend for documentation. Use 'man' followed by the command name and you should find at least a page on what you're looking for along with a list of other man references that could help.