Obviously the two are not fundamentally opposed to each other, but does the Bible offer any general guidance as to which should predominate in the focus of planning a worship service - edification of believers in attendance or of unbelievers/"seekers" who may be visiting?
“Many pastors and evangelism committees have come to agree that the public worship of God that attracts and spiritually benefits members will also attract and spiritually benefit non-members.”
“Worship and outreach are bound together because both of them proclaim Jesus. Therefore, worship and outreach are not mutually exclusive—to be pitted against each other. Nor are they substitutes for each other—as if you could replace worship with outreach or outreach with worship. Statements like “The Lutheran style of worship doesn’t connect with the unchurched” and “Outreach has no place in worship,” both miss the point that worship and outreach are joined inseparably, because both revolve around the teaching on which the Church stands or falls.”
The question you ask requires an extensive answer, and there some good resources that address your question.
The first quotation is from Christian Worship: Manual. It contains a brief chapter on “Worship for Evangelism and Outreach.” Your church library may have a copy. It is also available from Northwestern Publishing House. The quotation is from page 109.
The second quotation is from “Worship and Outreach: A Lutheran Paradigm.” It is available from the Wisconsin Lutheran Seminary Essay File. The quotation above is from page 5 of the essay.
You might also be interested in another essay on the topic: “Worship and Outreach: An Observable Synergy.”