Both offer multiple categorisation and both seem to work in that respect.
(Neither offers any categorisation of the categories themselves.)
Radio is a software license fee, with no service hosting – the software runs on your own machine.
TypePad (Pro) is a more expensive service fee , inlcuding hosting of the blogging service as well as the public blog pages.
TypePad (Plus) is cheaper, but has no html editing of your pages – so is much more limited format-and-content-wise.
TypePad has successfully migrated across all my existing blogger content.
(All existing internal permalinks still point to the blogger site unfortunately.)
(Radio has no tools to perform the same trick so far as I can see.)
Radio is infinitely flexible because all the files and s/w are on your own machine.
Radio has few wysiwyg tools so you need to be confident in using XML / RSS / CSS etc.
Radio also means you take on all the web server operation reliability and security yourself.
The point of TypePad (as opposed to full blown MoveableType) is to avoid this server overhead
The remaining problem with either is the fact that I must keep the psybertron.org domain active since there are so many existing links and a great coverage established in search engines, impressive indexing by Google included. My current ISP / Web-site Hosting combination (NTL and Tiscali) works fine and supports much more web-page content under the psybertron domain than just the blog, so it’s not simply a matter of domain mapping to the new blog location. It means publishing to the existing location, and maintaining that subscription too.
I need to think about the pros and cons, not just of Radio vs TypePad, but of staying put and waiting for Blogger (now part of Google of course, see above) to provide categorisation. What would swing the latter, would be if Blogger were to provide some additional features for organising and categorising the categories themselves. Come on Blogger / Google.
Decisions, decisions !