8-16 and 11-16 are pretty much specialized very-wide lenses. You can take pictures of people if you stand back at least 6-8 feet which means they don't fill up much of the frame. I would not want either as an only lens when I travel. That is where the 20-24mm ends of some of the UWA options come in handy. That's no ultrawide, just wide. SO it can work for more standard looking photos.
If you just want a pretty wide lens to travel with, I'd look at the 15-85. 15mm is quite wide for most kinds of photography, it has IS, ring USM and then covers the whole wide-normal-medium telephoto range.