The Gigaworks definately, THX certified and better generally better all round - maybe its down to the Twin Flared DynaPorts™, but who knows? The GigaWorks models are seen as the premium Creative speakers.
If you can get hold of anything Klipsch they will definately hit the spot for music and movies, with performance less orientated around gaming.
Personally, I use Logitech Z-5500s.
Also consider a soundcard upgrade if using onboard or something along the age of a SoundBlaster Live! That also helps
