It's not always easy being Sirius (NASDAQ:SIRI). Last night, the satellite radio upstart announced that it had surpassed the 400,000-subscriber mark. In a vacuum, that's great news. Every listener the company signs up is another step towards viability.

However, it's the upstart's misfortune to report this a week after rival XM Satellite Radio (NASDAQ:XMSR) announced that it had nearly 1.7 million subscribers. Yes, XM had a head start. So what?

Motley Fool Stock Advisor recommendations Amazon (NASDAQ:AMZN), eBay (NASDAQ:EBAY), and Netflix (NASDAQ:NFLX) all were accused of having head starts, and no one seems to remember who came in second. And the fact is, XM signed up more than 320,000 new subscribers in the most recent quarter. It has taken Sirius nearly two years to get to 400,000.

Sirius does have a few advantages over XM. It does. It sports a stronger balance sheet. It has developed superior content programming when it comes to pro sports. Its satellite situation is more stable. It draws a larger sum when it comes to average revenue per subscriber. Those are valid strengths.

No, Sirius isn't doomed. This market will continue to grow as people become enamored with the prospect of commanding over 100 digital channels. There will be plenty of market-share pie to share. And while the steep losses by both players are troubling, they are par for the course during the customer acquisition phase.

As usual, it boils down to valuation. Is XM worth $4.2 billion? More importantly, with more than 1.2 billion fully diluted shares out there, is Sirius worth $3.7 billion? That seems like an awfully narrow margin given XM's considerable lead. It's not too often that a clear market leader isn't granted a more respectable premium. More often than not, it doesn't stay that way for long.

For more market leaders, check out Motley Fool Stock Advisor . Or tell us this: Is Sirius misunderstood or overvalued? Will the company catch up to XM? Which service do you prefer and why? All this and more -- in the Sirius discussion board. Only on

Longtime Fool contributor Rick Munarriz would gladly broadcast his opinion on more than 100 channels of digital radio -- if only someone would listen. He owns shares in Netflix but not of any of the other companies mentioned in this story.