is one DBI package better than another? We've been using whatever is linked from the mySQL site currently.

If you've settled on MySQL, then DBD::mysql is the correct tool. There's a DBD::mysqlPP, but that's just for places where the full article can't be installed. If you're thinking of other backends, then the DBD for most backends is pretty clear cut (DBD::Pg for postgreSQL, etc.)