There are definite benefits to having a wiki page as it creates a consistent learning and introduction experience for your users.
However, specifically wikipedia vs self hosted wiki have several pros and cons. What I find most important to think about is if you really want anyone on the internet be able to modify your specifically designed content or is control on the content important. You could try to block users on wikipedia from modifying but that defeats the purpose and main benefit of wikipedia.
You could also do the same on your self hosted wiki with only authenticated users being able to contribute their own content.