Below is the UK Metroguide showing the East Midlands map selected. This map takes up 7147 kB. So you wouldn't be able to fit any more than this into an 8 MB cartridge.
The next picture shows the Roads and Recreation maps. Here I've selected 20 maps to cover roughly the same area as the single map above. These 20 maps together take up 4035 kB, leaving plenty of room to add more maps to an 8 MB cartridge.
So why are the Metroguide maps so memory intensive? Because they allow you to Find addresses down to a particular house number. The R&R guides won't even find street names.
So if this search facility is important to you then you're probably better off with the MetroGuide and a 16 MB cartridge. Otherwise I'd have to say that the Roads and Recreation maps (which have the same degree of detail on the roads themselves) represents the most flexible option.
