I don't usually recommend the S2 to anyone... if you want a two channel mixer, you probably want it even cheaper and may even be fine with the software bundled with it. I do recommend the S4 to people that are on the fence about how far they are going to expand later. The appeal of timecode and raw features in a four channel controller out of the box is too great. I like the VCI-400, and would recommend it, but if someone has no software, no controller the S4 is the better deal for the aspiring bedroom dj that will last them a long time and grow with them. Given that most of the people asking what controller to buy are going to spend most of their time playing to stuffed animals, the S4 seems like a great choice as there is little they will have to do but plug it in and rock out.
Personally I'm on the fence between VCI-400 and S4 in my recommendation to myself, if I can pick up an used one of either I am going to give it a go.
