If the criteria is "for a tech job", then move to San Francisco. The environment here and the learning on offer is unparalleled. And when I say learning I mean good, bad, indifferent, easy, hard, etc.
This is not to say you can't get those elsewhere, but the density here makes it more likely and more intense. A few years at a couple of SF tech companies is a decade of experience elsewhere. The tech companies here are in all different industries, sizes, stacks.
I say that coming from Australia, living full-time in SF - and still openly struggling with the lifestyle here now and then.
If you're trying to balance lifestyle, then I'd follow the other comments here -- Melbourne and Sydney are both terrific cites, great lifestyle and accessible culturally, but still different enough for North Americans to be interesting. The tech scene is still early, but growing rapidly. I haven't spent much time in Austin, but that feels like it may have similar attributes.
I quite like Denver/Boulder and Seattle too, but you might find that's not a huge enough departure from Toronto.
If you like big cities, New York or London might suit. If you're not a fan, then you'll be paying all the big city costs (rent, lifestyle) and getting zero back. London can be particularly tough. London might be worth it if you want a base to explore Europe. Otherwise can be a hard city to live.
Western Europe could be fun too, but the tech scene is much more varied and patchy. If you're looking at, say, Paris or Berlin, then you'd really need a passion for those cities. Plus I'd also suggest you'd want to narrow down to the 2-3 companies that you'd want to work for there -- i.e. the company first, the city second.
See also: https://hired.com/state-of-salaries-2017