It has been reported in a research by Roy Baumeister and Julie Exline that self-control temporarily weakens after exertion, replenishes with rest, and becomes stronger with exercise.
Self-control is an ability to subdue impulses or to regulations one's emotions, thoughts, and actions in order to fulfill specific (longer-term) goals, especially when faced with temptations and impulses. This enables a person to plan, evaluate alternative actions instead of getting carried away by impulses, and prevents him/her from behaving in a way that he/she might regret later on. Willpower is the ability to exert self-control.
I would say that knowing how much your rate will go up after the introductory offer would be the most important of these choices. The others are features that you might not use at all. The interest rate on your purchases would be the one that affects you the most.
