On the left hand side of the Garmin product page, you can find a typed description of base map data:
Legend for Canada
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The standard map coverage includes:
1. Oceans, rivers, and lakes (greater than 30 sq. miles)
2. Principal cities and many smaller cities and towns
3. Major interstates and principal highways
4. Political boundaries (state and international borders)
Canada - In addition to the standard map coverage, it also includes:
1. Lakes greater than 5 square miles (Southern Canada)
2. Lakes greater than 10 square miles (Central Canada)
3. Railroads
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You can go to Garmins Cartography web site and use a viewer to look at their map data (unfortunately, Garmin does not seem have a viewer available for the base data sets of their mapping units). The World Map viewer seems to be roughly equivalent to what my data set shows for much of Canada (excluding a few major cities):
Garmin Cartography
I would really suggest (if you budget supports it) that you look at the new color units (much easier to read the maps) and which also have 3x more memory, faster processor, USB support, twice the battery life and support auto-routing of trips. But at twice the price.
The routable map data is about $110. With the map data you can look up addresses on both units, but, on the newer color units, have the GPS automatically plan your route and give your turn by turn directions as you drive--pretty neat!
You did not say where you live or travel--so I don't know how much memory you will need. In large metropolitan areas you will probably need more storage...For example, just one map tile (how Garmin organizes their map data) for San Francisco/Oakland/San Mateo/Hayward/Berkeley/Concord area is 7 MBytes--will just fit in an 8 MByte Etrex Legend (does not include the western sliver of SF--map tiles do not always bracket a whole city and you may need to load a minimum of two tiles to contain the region/city you are interested in).
If you are only planing on using it in Alberta--my older map data allows me to load the entire southern Alberta Province (coverage, at best is only ~60 miles north of Calgary) in only 3 MBytes. The only city that had any city street level mapping was Calgary (that I could quickly find--the newer data set does appear to have better coverage of Alberta--the newer data sets will be larger--but you should still be able to fit much of your needs even in a smaller unit's memory)... Check the Garmin Cartography site for the various map sets and see which one works better for you (for example, perhaps a Canadian Topo map may list more roads--probably unnamed--in your region--but Topo maps generally don't support auto-routing on Garmins--but you can load both types of maps, if you have the room, and switch between them--depending on which is more useful).
The older back and white hand held maybe sort of useful in a city--but it will be difficult to use/see while driving. Also the newer units support USB (probably only on a windows PC) which gives much faster downloads than the serial links on the older units.
Of course, in the end, it is really up to you what you need and wish to pay. After reviewing the data sets for Canada--it may be very true that autorouting may not be of much use for you in your local area and the more expensive units would only help you if you traveled in Calgary (or Edmonton and some points west of Calgary) or if you purchased Topo or other maps for your area.
-Bill