So far as I can see, both have their benefits and both have head scratching moments.
Magnolia
- Its pretty. Very superficial of me perhaps but its pretty. :)
- User Profiles so you have some idea who is creating these bookmarks
- You can associate your Magnolia account with other accounts like LJ
- Avatars (again more pretty then useful but it pulls in more of the social aspect/expression)
- Groups we multiple users can compile bookmarks related to a certain subject (while tagging and networking on Delicious may be similar, this feature appears to take it a bit farther into true collaboration)
- It saves a copy of the web page when you bookmark it so if the page disappears you can still access a copy
- Easier to search all tags ie find all bookmarks tag with "tea", not just within my friends
- In general a bit easier to navigate, certain features more prominent
- You can see immediately how many times a web page has been bookmarked and easily find the users who bookmarked it
- Toolbar add on makes it very easy to add bookmarks (though only on computers where you can download and install the toolbar)