There is quite a difference between the Gamecom 380/388 and the 780/788. The 780/788 is USB and has Dolby 7.1 which the 380/388 doesn't, the 380/388 uses a 3.5 mm jack instead. Basically you can use the 380/388 on more devices. As you have noticed, they put a "8" instead of a "0", its just a newer looking model, no difference in specs.
Hope this helps!