Big auto shows, like the North American International Auto Show (NAIAS) that will be kicking off in Detroit next week, are big spectacles designed to maximize media attention -- but they're also important opportunities for investors in auto stocks to get a read on their companies' prospects.

Why? Simple: The relative quality of an automaker's vehicles is the most important contributor to its competitiveness and ability to profit over time, and the big auto shows -- where automakers present the final versions of new products for the first time alongside "concepts" that showcase the company's current thinking about future products

That makes NAIAS -- one of the world's biggest and most important shows -- worth watching closely. So what can we expect?

A big debut for the Blue Oval
Ford (NYSE: F) will take the covers off its all-new Fusion sedan, an extremely important entry for several reasons. First, 2011 was the best sales year ever for the (old) Fusion, and Ford needs the new car to carry that momentum forward in one of the world's most competitive segments. Second, the new Fusion is expected to showcase an all-new "design language" that will influence the shapes of Ford models around the world over the next several years, and the company clearly hopes that it will generate a lot of excitement. (Those who've seen the new Fusion say that it's very good, even stunning, but we'll see.)

Like other recent Fords and in line with the company's "One Ford" business plan, the new Fusion is a true "world car" -- not only does it replace the North American Fusion model, it also replaces the Mondeo, a similarly sized but completely different Ford sedan sold in Europe. It's a very important model for Ford, and shareholders should follow its debut closely.

Interim steps for the General
Meanwhile, given that the brunt of General Motors' (NYSE: GM) product renaissance is still a couple of years behind Ford's, I expect a relatively quiet show season for the General. (Next year's show should be more of a big deal for GM.) But GM has said that it will show four new models at this NAIAS, including the Cadillac ATS, a small luxury sedan aimed squarely at BMW's segment-leading 3-Series.

GM has never managed to get traction in this category despite years of (mostly halfhearted) attempts. But its Cadillac CTS has done fairly well recently against BMW's 5-Series in the next-size-up segment, which suggests that GM isn't that far away from a competitive effort. And that gap will be closing: CEO Dan Akerson has made no secret of his intention to remake Cadillac into a head-on competitor with BMW and Mercedes-Benz over the next few years.

So will the ATS reach this (very) high bar? Akerson himself has hinted that the ATS may end up being more of an interim step, but a strong effort is essential to GM's longer-term goal of establishing Cadillac as a relevant, global luxury brand. Watch its reception closely.

GM will be revealing three other vehicles at NAIAS, it has said, but in a change from past practice what it won't be doing is using its trademark blue "GM" logo on any displays. This is in keeping with a view articulated by Akerson and GM's chief marketer Joel Ewanick in recent months that has become part of the General's corporate mantra: "GM" is just the holding company, not a brand, and it should stay well in the background while the company's real brands -- Chevy, Buick, GMC, and Cadillac -- take the stage.

A tease from Toyota and a hot Honda
Building on its green-car cred and the hybrid franchise established by its popular Prius, Toyota (NYSE: TM) has said that it will show a new plug-in hybrid concept, called the "NS4," at NAIAS. The word "concept" means that this may not be a production-intent car, more a window into the automaker's current thinking -- but showing a concept can also be a way for an automaker to gauge public reaction before making the heavy investments needed to turn an idea into a mass-produced reality.

Little is known about the NS4 aside from a teaser photo showing one of the car's headlights, but expect it to take the "plug-in" rechargeable-hybrid idea a step beyond the system in the newest Prius. Meanwhile, Honda (NYSE: HMC) will be showing a slate of new Acuras, including a "concept" that is thought to be a thinly disguised draft of its long-awaited new NSX sports car. While sales of a new NSX are unlikely to add big bucks to Honda's bottom line, sports cars tend to have a "halo effect" from a marketing perspective, adding perceived excitement and desirability to a manufacturer's more bread-and-butter models. That's something that Honda and its Acura brand could sorely use right now.

Honda will also show a coupe version of its Accord, which it's labeling a "concept" -- but which is expected to offer clues about the upcoming all-new Accord, due this fall, which makes it worth watching closely.

Last, but hardly least...
Finally, Chrysler will show its much-anticipated (and sorely needed) new small car, the Dodge Dart. Built on Alfa Romeo bones provided by partner Fiat (OTC: FIATY), the Dart has the makings of a strong entry in a space that has become exceptionally competitive recently. Will the Dart have what it takes to go head to head with the strong Ford Focus, Hyundai Elantra, and the longtime segment leader, Toyota's Corolla? Given the strength of Chrysler's other entries recently, it just might. Watch this space.

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