According to Aristotle, there are three modes of persuasion: 1) Credibility/Ethos, 2) Rationale/Logos, and 3) Emotion/Pathos. In sales & advertising, all three are important, HOWEVER, in my experience, there is usually ONE of the three modes that carries MUCH more weight than the other two.
For example, if you're selling a new kind of back massager, you might not need to appeal to someone's emotions or prove your credibility in the industry. Instead, all they want to know is that yours "might actually work". So tell them why yours is different, or how it's made that might make a difference to them, and you'll see your sales go up.
On the other hand, if your product/service is a deviation from the normal way someone behaves (like getting someone to pay $0.99 for an app), then you're going to need a lot more than just the facts.