Sirius XM Radio (Nasdaq: SIRI) investors can warm up to financial media, for a change.

BusinessWeek is shining kindly on the satellite-radio operator and other in-car gadgetry makers, including GPS giant Garmin (Nasdaq: GRMN), in suggesting that recent favorable catalysts bode well for new-car sales.

Between details of the "Cash for Clunkers" program that will be revealed next week, and last week's successful bankruptcy exit by General Motors, consumers will be armed with the incentives and confidence to spring for a new set of wheels.

I admit, thought, that I don't see the argument for Garmin. Too many smartphones provide free rudimentary road-mapping, and that reality is only going to increase as network speeds improve. Not everyone has a smartphone, of course, but a good chunk of that market either will upgrade to a smartphone eventually or probably couldn't afford a Garmin or TomTom GPS system anyway.    

The case for Sirius is slightly more compelling. If GM fans are inspired to upgrade to new GM cars -- or if the "Cash for Clunkers" program inspires owners of older gas guzzlers to trade in their rides for more fuel-efficient cars -- we're talking about a whole lot of new cars moving off the showroom floors, with factory-installed Sirius or XM receivers aboard.

This is good news, but it's not necessarily great news.

I still feel more confident about Sirius XM's long-term chances than I do about Garmin's, though. Yes, Garmin is the profitable one of the two. It also has a chunky dividend yield. Besides, smartphones will eat into Sirius XM's business, too, since media heavies CBS (NYSE: CBS), Time Warner (NYSE: TWX), and Yahoo! (Nasdaq: YHOO) all have free smartphone apps for Web radio.

However, Sirius XM's subscriber base should stabilize as the auto industry improves. Can anyone say the same for Garmin? That may be the key difference.