There are two competing modules that handle language switching for interface and site content:

Localizer: http://drupal.org/project/localizer
Internationalization: http://drupal.org/project/i18n

While they may be very different under the hood, their user-facing functionality seems similar.

Does anyone have experience with either or both? Any views on which is technically superior? Is one dominating the field and the other soon-to-be orphaned?

I'm working on a 4.7 site for a client, and want to select a language-switching module that will likely have good support and a future upgrade path.