Hello Dave,
Because offline defrag actually downsizes or shrinks the file size, it does
indeed create more free space on the hard disk and helps to provide better
performance. Offline is sometimes not recommended because of the downtime
and inaccessibility associated with being “offline”. If you or your clients
are not in need or you perform this at odd hours, I think this may be good
practice.

Danny Gallegos
Roland Schorr & Tower
http://www.rolandschorr.com