But the main difference between Word and WP is the amount of control you have over the appearance of your text. I forget the technical term for it, but in essence, WP is modeled on the very first wordprocessors, run on mainframes, which were more like programming languages. In fact, to think of it, WP works a lot like html, but is much easier.
Because of the extremely precise control you can exercise over text appearance, WP was for many years favored by lawyers and academics (all those weird fonts for footnotes, paragraphs, etc.) and the legal and a university fields stayed with WP long after Word achieved market dominance. The only reason Word achieved market dominance was that MS used illegal anti-competitive means of forcing Word on purchasers of Windows, and after a tipping point was reached, when most people have Word and companies and individuals have to communicate and use each other's documents, everyone basically had to switch to Word.
But WP is still the much better program in terms of control. For example, if you italicize a word or phrase in WP, you can do it just like as in Word by highlighting it and pressing the right button. But if you need to see where the italics are, you can press "reveal codes" and you see a little icon surrounding the word that look like this:
<ital>italicized words<ital>
Every single thing that affects text appearance has a code. You can see precisely where these codes begin and end, and can manipulate them. To un-italicize the word, for example, you can go into reveal codes and delete the code.
That's really the main difference. If you came of age with WP, then Word is almost impossibly clumsy to use. I write in WP and if I need to share it with a Word user, I just convert the WP document to a Word document, which WP has a function for.
On edit: Here is a good explanation. The author says that Word is "object oriented" and WP is "stream oriented":
http://www.wpvsword.com/wp11vsword11/http://www.wpvsword.com/reveal_codes.php