Here is a snippet of a conversation I had recently about why I use Radio over Manila:
"I use both Radio and Manila, but my primary weblog activity is in Radio. I've got Radio installed on my machine in the office and I've enabled remote access (one of the preferences in Radio--Craig Burton has a great tutorial on setting this up). That way I can use Radio from anywhere using the username and password I specify in the prefs. I also use a tool created by Mike Krus of Newsisfree.com called RadioExpress! that installs as a javascript "bookmarklet" in the favorites bar of the machines I use at work and at home. This allows me, when I am on a page I find interesting/significant, to select some text and click the RadioExpress! link, which takes the text I've selected from the page and places it in a preformatted entry in Radio, ready for me to add my comments. When I submit, it takes me back to the page I was working on. It has become a fundamental part of my daily workflow, and I couldn't do it if Radio restricted me to a one-machine publishing model.
The primary reason I use Radio over Manila is the capability of multiple-category posting. The fact that each category can be served up as an HTML page (even to a different server via FTP) or an RSS feed is wonderful, but I am most excited about the potential of the tool. I want to be able to designate a category that sends the content of my post to an email address. It could be an individual or a distribution list of some sort. Once I figure out this capability, my weblog tool becomes a much more robust part of my communication interface. Manila allows categorization via "departments", but only one at a time. Many of my uses for my weblogs demand the data be routed to multiple destinations. I'm hoping Manila inherits this capability from Radio soon... "