Reply to 4 channel vs 2 channel?

I have a questin to you guys out there when it comes to mixing....


1 - How do you use a four channel setup?...Do you use 2 decks+sample/remix decks?....in what fashion?
2 - When i see the S2 and the S4, the only diffrence is basecly 2 vs 4 channel, should i go for the S4?
3 - I know it basecly comes down to preffrence here, but i want your guys opinions, and how you use the 4 decks?...