You’ll notice these articles are in agreement with the same basic three questions to consider, but they complement one another in a helpful way.
Here’s the summary from the end of Keller’s article:
Your vocation is a part of God’s work in the world, and God gives you resources for serving the human community. These factors can help you identify your calling.
Affinity is the normal, existential/priestly way to discern call. What people needs do I vibrate to?
Ability is the normal, rational/prophetic way to discern call. What am I good at doing?
Opportunity is the normal, organizational/kingly way to discern call. What do the leaders/my friends believe is the most strategic kingdom need?
Your life is not a series of random events. Your family background, education, and life experiences—even the most painful ones—all equip you to do some work that no one else can do. “We are God’s workmanship, created in Christ Jesus to do good works, which God prepared in advance for us to do“ (Eph. 2:10).