Kaz, the Platinum's just have the external drive bay with all the neat-o connections. It uses the same sound card.
The SBLive! is a pig when it comes to CPU time, and Creative's drivers do not expose any hardware buffers at all in DirectSound. Simply put, it is not much better (if at all) than some dumb AC97 device.
The Audigy line is much better. The Audigy 2 is slightly better than the original Audigy in CPU usage. The Audigy 2 ZS is the same as the Audigy 2, except it has a little less noise and better dynamic headroom.
The difference between the Live! and Audigy line is night and day. When I swapped out my old SBLive! for an Audigy 2, I picked up 10 to 15 FPS in almost every game as the CPU is able to do so much more than before. Your results may vary......
Do not take this as a recommendation. In fact, I usually will recommend AMD users not to use any Creative products at all due to the number of issues I keep hearing about them.
Funny thing though, there seems to be no coorelation with the issues, except the motherboard has an AMD CPU.