Q: I looked through several forums and websites so I thought you would know. Is there any difference in the cable for a 3G iPhone vs a 3GS? It seems the price is a bit more for the 3GS.
A: There are no electrical differences between any of the iPod and iPhone USB to Dock Connector cables—a third-generation iPod USB cable from 2003 still works just fine with an iPhone 3GS. In fact, with a drawer full of random iPod sync cables to choose from, this is something we regularly do in our labs when connecting various iPod and iPhone models for testing.
Apple has made some minor design changes to their own sync cables over the years, including reducing the size of the Dock Connector end of the cable and changing the plastic coating, but none of these changes impact the compatibility of the cables with any Dock Connector based iPod model. Although design and packaging changes may have some impact, price differences between Dock Connector sync cables are mostly arbitrary.