Those genius gearheads over at Popular Mechanics have taken time out of their busy schedules test-driving monster machines and contemplating fuel made from algae to tackle something slightly more pedestrian: GPS.

Specifically, writer Mike Allen looks at the pros and cons of the high-end, dashboard-mounted GPS systems (which usually come only as part of a premium stereo package) versus the myriad pocket-sized, suction-mounted guides -- your Garmins and TomToms and the like.

As a blow to the slick dealer-floor salesman trying to upgrade you to one of those upsell packages, Allen comes out in favor -- overwhelmingly so -- of the little guys. And while he spends some time reviewing two different hand-held GPS units (the Mio C320 and a motorcycle-specific Garmin 660, if you're interested) versus the in-car unit of a Honda Insight, the more immediate take-away is his 11 points for portables versus only five (really, four and a "maybe") for in-dash systems.

Some of the pro-portables are obvious (they're cheaper and, um, portable), but some have more of the "oh, right, you can do that" feel, such as the fact that you can put your destination in the night before at the table rather than when you're sitting in your car (think about when you're so rushed you don't have an extra second, let alone a couple of minutes). You can also upload and download your trip information to your computer, and you don't need to pull over to the side of the road to use the system, as you do with in-dash units. On the plus side for the car-specific tech is the bigger screen, the fact that it can't be stolen out of your vehicle (something that, unfortunately, happened to my Garmin last year), and that it's tied to the stereo system in such a way that it will lower the radio's volume in order to give directions. If you're still thinking of dropping two grand on that in-dash unit, head over to the site to read Allen's full list of reasons.

It also got me thinking: Is there another amenity for a car that's so much better served by a mainstream product? Some people insist that speakers -- even the ones included with the fancy sound-system packages -- are never as good as what you can get aftermarket. Even then, though, you're nowhere near the cost and efficacy disparity seen with the portable versus in-dash nav systems. Can anyone think of a comparable example?