Complex sentence: The iPhone 3G and 2nd generation iPod Touch have limited features, including lack of multitasking capabilities and the ability to set a home screen wallpaper, while the iPhone 4, iPhone 3GS, 3rd and 4th generation iPod Touch have all features enabled, such as multitasking.
Split into simpler sentences: The iPhone 3G and iPod Touch (2nd generation) have limited features, including lack of multitasking capabilities and the ability to set a home screen wallpaper. While the iPhone 4, iPhone 3GS, iPod Touch (3rd & 4th generation) have all features enabled, such as multitasking.