In Brand Advertising which should be emphasized - Reach or Frequency?

Many will say that it is more efficient to focus on reach (versus frequency) because there are diminishing returns with each new ad exposure. That is, the advertising response curve is usually concave. This is particularly true if your goal is to create an immediate sale of a ubiquitously purchased consumer product. In that situation, reach almost always delivers "more bang for your buck." However, if your funds are limited and your audience is highly targeted, you would do better to focus on a reach schedule of 3+, seeking out media with significant audience overlap.

For brand building purposes, I usually focus on advertising frequency targeted at those that are most likely to influence the remainder of the market: primary target opinion leaders and "hard core" users.

(Source : Brand Strategy Insider)