The silicone rubber case wars continue with Griffin's new FlexGrip and FlexScreen cases, which share obvious similarities with XtremeMac's previously released TuffWrap and TuffWrap Plus cases. FlexGrip is a two-toned case with textured dots on the back, available for the third-generation iPod nano and iPod touch, each with screen/control film and a cleaning cloth. FlexScreen, by contrast, is a single-colored case with a front plastic shield, just…
