Does anyone have a strong preference between Bugzilla and RedMine (free defect trackings systems)?
They are slightly different systems, and they were built with different objectives. Bugzilla is devoted to bug and issue tracking, and it is very powerful in that perspective. Redmine is a little bit more general, and although it offers less capabilities when dealing with issue tracking, it gives you a lot of other features as well (e.g. wiki, SCM integration, lightweight document management, and so on). I’d choose Bugzilla if I had to do just issue tracking or if I already relied on other tools for that additional capabilities. I’d go with Redmine (or Trac) in all the other cases.