Google Docs, for sure. Zoho just feels strange to use, and their UI is just atrocious, to be honest. Google Docs gets the document organization on the dot (Zoho... botches it) and gets usability and lightness of the user interface correctly. Lastly, the collaboration features are better than Zoho Writer's.
I still kind of prefer some aspects of the Writely UI (http://jaman.ca/files/images/writley-snap.JPG), but the new changes to the Google Docs UI make it awesome (especially the fixed-page-width view.)
I still kind of prefer some aspects of the Writely UI (http://jaman.ca/files/images/writley-snap.JPG), but the new changes to the Google Docs UI make it awesome (especially the fixed-page-width view.)