Modern evangelicals would answer this in a variety of ways. Some would say the level of gifts or intellect the preacher possesses. Others, would reference the quality of a man’s formal theological training or his oratory skills.
Let us allow A.W. Tozer to cut through the superficial and cultural emphasis of our day in regard to preaching with these insightful words:
Let me shock you at this point. A naturally bright person can carry on religious activity without a special gift from God. Filling church pulpits every week are some who are using only natural abilities and special training. Some are known as Bible expositors, for it is possible to read and study commentaries and then repeat what has been learned about the Scriptures. Yes, it may shock you, but it is true that anyone able to talk fluently can learn to use religious phrases and can become recognized as a preacher. But if any person is determined to preach so that his work and ministry will abide in the day of the judgment fire, then he must preach, teach and exhort with the kind of love and concern that comes only through a genuine gift of the Holy Spirit—something beyond his own capabilities