Scenario: Assume your grandmother is going on a long roadtrip involving a long stretch of road in an unpopulated area. From a usability perspective, is it better for her to have a cell phone with her, or would you rather explain to her how the road-side emergency phones work?
aspects to consider
functionality: what are the most important tasks
performance: how good are the products at those tasks
capabilities and background of the user
environment: external factors that influence the user experience