I haven't tried coded or Retrospectiva but I've used both redmine and trac, and in my opinion, redmine is better because:
- Easier installation for multiple projects
- Out of the box support for git and mercurial
- support for remote repositories
- support for LDAP authentication
- built in web based administration
- many good plugins available
- and a better looking default theme if you care about that
Initially I was more familiar with python than ruby, so I tended towards trac the first time. But redmine is much more powerful, with more features out of the box, and with a greater community of plugins available.