There is no difference. You may use any standard ipod/iphone/ipad cable with any of the devices.
The only difference is they now have two cables the 30 pin dock connector cable and the "lightning" cable. The lightning cable is only on the LATEST generation of devices (ipad mini/4, ipod nano 7th gen, ipod touch 5th gen, iphone 5)
Chances are you have two dock connector cables, you cant mix them up cause they're the same thing.