I have three versions of the software.
Australian City navigator-This is optimised for use with the 26** series of GPS.It's supposed to have the best coverage for turn by turn navigation.
Europe City select V7-This still has turn by turn but not as complex as the Navigator.It was a hell of a lot cheaper than the Europe Navigator an suits my purpose fine.It still has all major and minor roads.
Worldmap-As you say, it covers the whole world, but only major roads.It does cover out of the way places though,
Northern pakistan and India for instance.
Metroguide-I dont have, but I believe it covers areas such as fire trails and the like.Only covers small areas because of the detail and doesn't offer turn by turn.
I think all this is correct and hope it helps