i3 will use different workspaces for each monitor. So if you have dual monitors by default, the primary monitor will be workspace 1 and the secondary will be workspace 2. Workspaces are created and destroyed as needed, that is they're existing only when windows are attached.

One problem I had with Awesome is that sometimes pop ups from Chrome on one monitor would end up on another. I also had trouble switching focus between dual monitors. As a result, I would need to use my mouse. i3 multi-monitor support is more seamless compared to Awesome.