With the Rhetorical Triangle, every piece of communication is essentially a trilateral relationship. (The Rhetorical Triangle is something they teach at universities and colleges quite a bit.) Between Logos (rational appeal), Pathos (emotional appeal), and Ethos (ethical appeal), success of any communication is responsible in part to the influence of these three appeals combined with context. When it comes to applying these principles to the marketing world, a critical driver of your language is your understanding of the marketability of your product.
According to Richard Vaughn, and the FCB grid (more info available here), products typically fall into two different categories: Think or Feel.
A Think product is a product where a consumer heavily weighs their purchasing decision. This often includes plenty of product research and other personal efforts before purchase.
A Feel product is a product where consumers are primarily driven by their emotions when making their purchasing decision. This often means that the purchase was/is not premeditated and is guided by quick decisions and need/want processes.
Next, these two product categories fall into two levels of involvement: Low or High
Low involvement means that the products tend to be purchased based on impulse and quick decision-making. With a relatively low-price point, consumers don’t consider their purchases to be high risk therefore they are low involvement.
High involvement means that the products tend to be purchased after much consideration, research, and assessment has occurred. Frequently, these are higher cost items or products that have invested staying power.
Depending upon the Think/Feel and High Involvement/Low Involvement categories, content strategy can be narrowed to fit the correct audience and make its appeals rooted in the rational/emotional spectrum.