If you link to external (not BU server) it saves bandwith
if you link to files allready elsewhere on the bu server you only "lack" the feature of disallowing direct linking and counting through the filebase.
one feature of the filebase is the counting of downloads, which is only reliable if all downloads are made using the filebase "download file" button. but that can be done by analysing the apache logs as well, so the feature is only to present the stats to the user/downloader on the fly and make rankings by download popularity.
a nice-to-have thinggy.
btw. you can simly "move" the files to filebase/uploads/
/.. and then add/edit the link in the filebase db.
i'm working an automatic filesize detection, which will add this information to the database, the sql query is allready 40% ready...
until its done automatic, it is a filed which te uploader should fill with some reasonable data.
cheers