It’ll depend completely on the city and surrounding area. Canada is much
closer to the high-tech stuff in the US. But of course, if you can speak
the appropriate language(s), Australia is much closer to the high-tech
stuff in Asia.
As has been mentioned, there’s a big (in Canadian terms) concentration
of high-tech around Ottawa. However, the real center of Canadian
cultural and commercial activity is Toronto (no, I’m not a Torontonian,
it’s just the truth). If the high Quebec taxes are not a deterrent, I’d
suggest that Montreal is probably the optimal combination of high-tech
opportunity, cultural amenities, and general quality of life. Other
things being equal, it’s probably where I’d go were I to move back to
Canada, Toronto would be a close second.
Vancouver is supposed to be a very lovely city; it isn’t. I’ve lived
there, and architecturally Vancouver is somewhere between bland nouveau
West Coast and drop-dead graveled-yard ugly. The surroundings are
beautiful, but even then, be prepared for very damp, gray, depressing
winters–if sunshine is important to you, don’t move to Vancouver.
Canada’s general social attitudes are much more European than American
(and the general Canadian attitude towards many current US policies is
probably best described as somewhere between amusement and disgust), so
if you’re a strong libertarian-type hacker, you may not like that aspect
of Canada. (Personally, I like it quite a bit.)
Australia will be warmer. Much warmer. And sunnier.
Hope this helps,