The user has to select from a pool of items or options. What items are displayed and their order or sequence may have some relevance to the user.
In some cases this list must be accessed on a regular basis, on others very rarely.
[Small wireframes of picker and two-lists]
Determine when the user will need to access the pool of available items.
If the number and order of items will changed infrequently, use the Picker Dialog.
If it is likely that the items will be changed on a regular basis, use Two Lists with Arrow Buttons.