The UIPickerView class implements objects, called picker views, that use a spinning-wheel or slot-machine metaphor to show one or more sets of values
UITableView is a class used for displaying and editing lists of information on iOS
"Uitableview is much more customizable than uipickerview"
from question "Is it good to show a UIPickerView with only small data size?"
"The uipickerview is nothing more than a uiview with one or more uitableview and background and selector views"
from question "Customize UIPickerView's Skin with images"