Take a look at Starbucks. You never saw any advertising for Starbucks when they were starting. They built their entire brand with PR. Advertising now maintains the brand.
When building a new brand, it might be the smarter move to work on PR first.
Let's face it, you need to have publicity if you want to really grow your brand. Publicity gains credibility by virtue of the medium
There is a lot of noise in the world, commercials, billboards, and spam. People are interested in news, tips, things that add value and don't necessarily sell. PR brings about awareness. Awareness of you, your product or service is the first step to gaining a new client or customer.
PR also brings about credibility and trust. It's a fact that most people do not trust advertising, but they do trust the press.
PR engages your potential public and let's them know who you are, let's them know about your product or service and let's them get to know you in a safe, non-selling environment.
You are doing yourself and your company a disservice if you don't take a look at this. PR and Marketing are related and work together.