Think of the Dev channel of Google Chrome as an alpha build, Chrome’s equivalent of Firefox Aurora. It’s one step forward from the untested nightly builds of Chrome Canary, but it’s still a long way from the finished article, never mind the more reliable beta.
That said, Chrome Dev obviously remains a key part of the Chrome development cycle, as it’s the first release specifically designed for wider public consumption. Unlike Canary, you can’t run Google Chrome Dev side-by-side with the stable, final version, although you could fashion your own clumsy workaround by running Chrome Dev alongside the portable version of Chrome.
If you do go down the Dev path, be prepared to enjoy a much less stable experience, although in return you’ll be testing cutting-edge features that won’t be available to other users for weeks if not months.
Chrome 642 is now in the Dev channel. Note that the Dev channel and should be used with some caution.