The two satellite radio upstarts continue to carve up the sporting world.

XM Satellite Radio (NASDAQ:XMSR) has hooked up with the PGA Tour to provide exclusive live event coverage, rental and sales of XM2go radios at PGA tournaments, and a dedicated golf channel to which fans can tune for exclusive programming beyond the 18th hole. The long-term broadcasting and marketing agreement was announced yesterday.

Ever since XM announced that it was hiking its monthly fee to $12.95 to match rival Sirius Satellite Radio (NASDAQ:SIRI), the market has been waiting to see what XM will do now that it can no longer compete on price. XM started out the year with 3.2 million subscribers, nearly three times more than Sirius. Now that it has leveled the playing field, it will have to outdraw Sirius with new content signings to avoid losing its significant early lead.

Sirius has chalked up major scores in landing Howard Stern, the NFL, and wrestling NASCAR away from XM (although that won't happen for another two years), but XM's major coup so far had been scoring the exclusive satellite radio broadcasting rights for Major League Baseball. When the PGA Tour Network debuts this summer it is unlikely to topple the popularity of XM's baseball content. Still, it helps differentiate XM from Sirius and that's important.

A "hole in one" may be golf's greatest play, but it's not much of a compliment if it's your business model. While XM and Sirius have already carved up the major car manufacturer market so that each automobile company is aligned to just one company for factory-installed systems, it's a different world in the after-market. When someone walks into Best Buy (NYSE:BBY), they have a choice to make and the exclusive content will be the determining factor.

While more than 60 channels of commercial-free music apiece is a great selling point that gets the consumer to migrate to satellite radio in the first place, there is still a choice to be made. While Sirius can claim to have the more notable disc jockeys and XM brags about its deeper playlist, these aren't deal breakers or deal makers when it comes time to pick one over the other. Really.

That's why it's important for both XM and Sirius to continue to win over traditional radio's biggest celebrities. That may even be more critical than the sports contracts because those are the one-two punch deals in which XM and Sirius gain a popular voice, while simultaneously subtracting that card from free radio's diminishing hand.

So, sure, putt away XM. Avoid the sand traps. Aim for the green. But truly exclusive content is the name of the differentiation game. Swing well on that front. It's the way respectable Rule Breaker growth stocks play to win.

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Longtime Fool contributor Rick Munarriz thinks it's cool that Sirius broadcasts The Motley Fool Radio Show four times over the weekend. He does not own shares in any of the companies mentioned in this story. The Fool has a disclosure policy. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.