Unique role, not better, just different
When we say that the missionary fills a unique role we do not imply that he is better than others, simply that he is different. He is not necessarily more spiritual than the pastor, or even the layman, who remains at home.
Nor will his reward at the judgment seat of Christ be any greater. He is the servant of Christ and will be asked the same questions and judged on the same basis as anyone else.
Did he seek to promote his own glory or was he concerned solely for the glory of God (1 Co 10:31)?
Was he motivated by some personal considerations or was he constrained by the love of Christ (1 Co 13:13)?
Did be do his work in the energy of the flesh or in the power of the Holy Spirit (Acts 1:8)?
If he can answer all three questions correctly he will have his reward; otherwise his work will be judged to be wood, hay, and stubble to be consumed in the fire (1 Co 3:1215). The missionary is not better than his fellow workers, just different.
J. Herbert Kane, The Making of a Missionary