There is a certain convenience with the ad exchange. Plugging in as an advertiser can be relatively quick and simple, the CPM rates are low and there are varying targetting options that can give you a decent mix to help test your strategy.
But its convenience comes at a cost. The low CPM rates usually signify non-premium inventory that the publishers have had difficulty selling themselves. In fact, more often than not, the ad units being sold are placed at the bottom of the page or “below the fold” of a screen monitor, counting an impression even though the ad was never actually seen. You can occasionally find premium inventory but the CPM rates tend to be priced quite highly due to the ad exchange’s commission, so you’re better off just going direct.
Furthermore, when you plugin to an ad exchange, you don’t necessarily know where your ads will be shown. Your ads could appear on a publisher page discussing an unsuitable and sometimes even undesirable subject, like terrorism or world hunger. This can potentially create an unwanted, unconscious link between said subject and your product. When you go direct, you know exactly what website, what page and what unit your ad is displayed on. You know what kind of audience you’re targetting, giving yourself an opportunity to tailor your campaigns in order to improve your conversion rates and grow your business.
The brand awareness element of direct deals are more lucrative than one would think. When advertising to a targetted audience, the chances of somebody recalling your brand in the future and searching for it increases since your product is intertwined with their interests, at least indirectly. So while your click-through rate may be the most standard metric when evaluating your campaign, your view-through rate, although hard to measure, accounts for your overall results.