> Texas is also building high-speed rail, which will end up linking all of their major cities, an immense bonus.
Denver already has light rail connecting the airport, Boulder, and Golden as well as other metro areas, as well as amtrak, shuttles, and other public transport to the mountain regions for skiing and other recreation. It's also among the most bike-friendly cities I've seen in the US, with routes extending extremely far and having a vibrant cycling culture. Workers commute with all of these options every day.
For being a smaller metro, Denver-Boulder's tech scene is much more vibrant than DFW's. Amazon _already_ has tech offices in both Boulder and Denver.
Among Texas cities, Dallas also doesn't have the tech talent pool and established network of transplanted tech companies that Austin already has, let alone the politics that many west coast tech workers (and Bezos) find attractive (although that point is kind of moot, because either way it's still Texas).
I don't really think it's going to be Denver, either. I'd be really disappointed if it's Dallas. I expect Chicago, Boston, DC, or Atlanta.