The contestants are two satellite radio companies with big-name backers and deep pockets, hoping that every music- and talk-loving citizen will shell out $10 to $13 a month for their services. In one corner: XM Satellite Radio, on the streets since September. It's financed in part by familiar names like General Motors, American Honda Motor Co., Clear Channel Communications and DirecTV.

In the other: Sirius Satellite Radio, the inventor of satellite radio technology, just now hitting the airwaves. It's financed in part by DaimlerChrysler AG and Ford Motor Co.
Sirius has been available in Michigan for about two weeks, which gave us just enough time to give it a thorough test drive. It's live now for the most part across the country but will finish its final rollout in metro areas by July 1.

We drove with XM Radio, available nationwide, for several weeks earlier this year.

So which should you buy? Let's start with the basics.

Satellite radio's digital broadcasts are available anywhere in the country, so people who live in rural areas without a good radio selection are a natural market. So are truckers and others with long commutes who don't want to change the channel regardless of how far they drive.

Others who don't have coverage issues with their current favorite stations are likely to be wooed by satellite radio's vast selection of channels and CD-quality broadcasts.

One nifty benefit of a digital service is that artist and title information is sent along with the audio broadcast, so satellite radios nearly always tell you what's on.

Both Sirius and XM offer at least 100 channels of music, talk and entertainment. Both offer stations dedicated to particular decades of music (1940s-1990s), though each is structured slightly differently. Both offer a wide variety of pop, rock, country, urban, jazz, Latin, classical and other musical genres (though it's worth perusing the full lists to make sure the service you pick has a good selection of the music you like).

And both offer 30 to 40 talk stations, ranging from sports to news to education to entertainment.
Sirius' music stations are all commercial-free because they're all produced in the company's New York studios. Some XM Radio stations are commercial-free (produced in Washington, D.C.); others are rebroadcasts of traditional radio stations and include commercials.

Both have some limited commercials on their talk stations, mostly promotions for products or broadcasts by those who produce the stations.

In our unscientific survey of the two services, XM channel hosts had more personality and were more entertaining. However, Sirius' talent clearly knew their genres, commenting knowledgeably on virtually every song played.

But many folks will choose a service based on the agreements the companies have made with their talk-radio station partners.

Sirius landed the big one: an exclusive agreement with National Public Radio, which offers two stations plus a Public Radio International feed only on that service. It also has the Outdoor Life Network, A&E, Scifi.com, the History Channel and Biography.

XM has deals with USA Today and NASCAR Radio, while both services offer Radio Disney, Discovery Radio, E!, ESPN, CNN, Fox News, the Weather Channel, CNBC, Bloomberg business news, ABC, C-SPAN and the BBC. Both offer Spanish-language programming. We preferred the entertaining mix of mainstream rock and pop broadcasts and hosts on XM. But Sirius' mainstream broadcasts were adequate, and their other programming produced in-house was more diverse. Who would have known that I would have become a devotee of the Swing Channel? The bottom line depends on the broadcasts you like. For XM Radio, visit www.xmradio.com and click on Programming, then Full Channel Listing for its roster. For Sirius, visit www.siriusradio.com and click on Programming, then See All Channels.

We were unable to draw final conclusions about the relative sound quality of the two services because of the differences between the radios we tested.

For XM, we tested a Sony Plug and Play unit, which has an adapter that plugs into a cassette deck, like the original CD players. For Sirius, no portable unit was yet available (one is due later this year), so we tested two hardwired units installed in a sport-utility vehicle and a sedan.

Sirius says that its satellite technology, which constantly adapts the way channels are broadcast, results in superior sound quality across all stations. A top-of-the-line system installed in a luxury sedan was overwhelmingly impressive, with no differences between station broadcasts and compact discs even at extremely high volumes.

But even the portable Sony XM unit retransmitted through the cassette deck of a sports car sounded dandy, rivaling CD tracks and the second Sirius system in quality.

Our conclusion: Either system will give you high-quality, digital broadcasts that shouldn't offend even dedicated audiophiles. The differences you notice between the two systems will likely depend on the level of stereo system you install to receive them.

Both services occasionally suffered from the curse of satellite and cable television (with apologies to Bruce Springsteen): 100 channels and nothing on. But after working with XM for a couple of weeks and then returning the unit, I went into withdrawal from my lack of crystal-clear broadcasts and artist-title information.

Which service will I choose? It's an extremely hard decision, but I'd probably go with Sirius. The wide variety of original programming and lack of music-station commercials won me over, even though some of its DJs need personality transplants. I'd even be willing to pay the higher monthly fee ($12.95 versus $9.99 for XM). But I wouldn't be unhappy with either service.

Satellite radio is definitely here to stay. If you spend a lot of time on the road, you owe it to yourself to listen in on what it has to offer.