Well in a lot of ways the different provinces of Canada are like different countries, and then within the provinces there is a lot of variation too, so you need to know what you are looking for. You can't just ask "what is Canada like" as it were, because I don't think you will get a very meaningful answer.
We have been living in BC for six months and personally I think it is fantastic, but that doesn't mean you would like it at all.
So you get to choose between the Maritimes, which are the closest to the UK, and traditionally I think relatively poor. Quebec, which has a very different culture because of the French influence; Ontario, which is the "hub" of Canada I guess, and the most built up (although like the rest of Canada that is only the Southern part), more multicultural and diverse, and has a bit of a superiority complex; the Prairies, which are very flat and very cold (people move from there, not too there, I'm told); Alberta, somewhat conservative, and normally booming (like the American states below it it has quite a can-do type attitude, which you may find either bracing or alienating depending on your point of view); or BC which is very West Coast (beautiful, relaxed, and a bit hippyish at times) it also has a big Asian community in Vancouver, which is another cosmopolitan city; then there is Newfoundland, which seems to be thought of in the same way we might think of the West Country, like a bit of a strange cousin. If you really like the cold there are the Territories
That quick run down is a summation of the views of the people I work with btw!
All the major cities generally do pretty well on the "good places to live" lists, and the population density depends on how far from the border with the States you are really. All of the provinces are fairly sparely settled away from the big cities (that is Toronto, Montreal and Vancouver).
A significant factor is how far away you want to be, and the time zone differences too. For example, from where I live in the interior of BC it would take 12 or so hours to get back to the UK and there is an eight hour time difference. Whereas from Halifax (Nova Scotia) it's currently three hours time difference, and a 6 hour flight. The cost of getting home will obviously vary too.
The weather is something to consider very seriously too. The central provinces get very cold (down to -40 in Winnipeg for example), and stay that way for a very long time (with significant snow on the ground for months). Some people find that very difficult to adjust to. I live in the hottest city in Canada, and we still had a few weeks of -20 this winter. Now it's summer it is gorgeous though (and the snow was fun).
Regarding the bilingual aspects, then obviously Quebec, but also some of the Maritimes have large French communities, and Vancouver has a lot of Cantonese!
Geography is another significant consideration. BC is mostly mountains, lakes and trees (except where I live, which is semi-desert) with a great cast line. The Prairies and Alberta are flat (and I mean seriously flat!), Ontario has lots of big lakes, and then the Maritimes get mountains and coast line again. I think both coastlines are pretty beautiful. Bear in mind it is all big in a way that is quite difficult to comprehend. We drove from coast to coast when we moved from New York, and it took us two and a half weeks of pretty solid driving (7-8 hours most days).
Price wise, if you are not working, I would guess that the cheapest areas are the Maritimes and the Prairies. BC is relatively expensive, and Alberta's boom has pushed prices up there.