Angular-ng-options-vs-ng-repeat.md

<select placeholder="Select">
  <option
    ng-repeat="u in users"
    ng-if="u.name != user.name"
    value="{{u}}">{{u.name}}</option>
</select>

<select
  placeholder="Select"
  ng-model="taggee"
  required="required"
  ng-options="u.name for u in users | filter: removeUserSelf">
</select>

Dropdowns made with ng-options allows the selected value to be an object, while dropdowns made from ng-repeat has to be a string.

Src: http://www.w3schools.com/angular/angular_select.asp