For my Wiki experience I chose to work with the ASH 23 Things Wiki to add an entry. You can link to it here: http://ash23things.wikispaces.com/Favorite+Vacation+Spots. I added an entry to the Vacation Spot place and wrote about Monteverde, Costa Rica.
This particular wiki was very easy to work with. I had no trouble figuring out how to edit, add pictures, and change font color. I've created wikis before using a different program (can't recall the name at the moment), and it proved to be cumbersome. Editing was difficult, setting it up was tedious, nothing was essentially easy. So I was happy to find that this particular one was easy to work with.
In terms of comparison, wikis work well when you need a discussion format. Although I have to be honest and say that the forum function on Moodle works fairly well. Plus, I sort of prefer it because I can comment and grade a forum post. So, I don't use wikis very often. I found wikis useful when preparing for Project Term. It was an easy and creative way for students to post their research on the country prior to the experience. Plus, they could add pictures, which is always a plus.