The best way to review products meant to be used out in the trenches is to hit the trenches with those products in tow, going head-to-head in practical (preferably emergency) situations. In this case, we're talking iPhone cases that recharge your smartphone while protecting it.

Our two combatants in this intensely unscientific test are the Scosche Switchback Surge G4 backup battery case with kickstand for iPhone 4 and the PowerSkin recharging soft case.

The battleground was the parade for Chevrolet's 100th anniversary, part of the 2011 Woodward Avenue Dream Cruise car weekend in Detroit. With more than 1 million car lovers flocking to Motor City to view more than 40,000 custom cars, opportunities to take photos and videos were more prevalent than Chevy Small Block V8 engines. To the non-gearheads, there were a lot.

For two straight days, morning until night, I cruised Woodward in a 2011 Camaro as elite and custom cars came and went. Taking all of those photos and HD videos drains an iPhone's battery fast. So, I went into that crazy traffic jam with both the Scosche Switchback Surge G4 and the PowerSkin charged and ready. I tested how much protection they provided, how long they lasted, and how well they recharged an iPhone in constant use.

For the uninitiated, these cases hold a battery pack and the standard iPhone USB connector. The case's interior plug locks into the iPhone charging port as any charging cable would, transferring that backup energy supply to the iPhone.

The Switchback is a hard case equipped with a kickstand for easier video viewing. But I was taking videos, not watching them. I needed the Switchback to recharge my smartphone quickly and to give me significantly more battery life for my endless use of the camera.

Fortunately, the Switchback did that, effectively doubling the overall maximum battery life of the iPhone. Under maximum use with constant videography and photography, my iPhone 4 lasts between one hour and 90 minutes. With the Switchback in effect, I was taking photos and videos for almost a full three hours.

The Switchback provides more complete protection than the PowerSkin, providing a high-impact shell around the phone. Its primary drawbacks are its weight--which almost doubles the heft of the iPhone--and its size. With its double-shell construction, you end up with a longer and thicker phone, sacrificing the sleek iPhone design for more battery life.

The PowerSkin doesn't offer the same level of protection, but its rubberized, soft case design (hence its name) makes it lighter and thinner. When I exhausted the Switchback, I switched over to the PowerSkin without difficulty. It charged the iPhone with the speed of a cable connection and also doubled the video and HD camera's life. In fact, while this isn't independently verified, the PowerSkin drove the little camera for 30 minutes longer than the Switchback.

Regardless of whether you need to take photos of 40,000 cars, the choice between these two recharging cases comes down not to their near-equal charging capabilities but to their secondary qualities. If you want maximum protection, go with the Switchback. If you want a lighter, sleeker phone in your pocket, the PowerSkin offers the better option. Both cases sell for $80 and are available online and multiple retails outlets.