what boards have you ridden before? weight? riding ability? most of the boards you are asking about are rockered. any particular reason why?
He said he'd like his board mostly for rails so I'd say that's why he wants rocker. To the OP, I had a K2 WWW and loved it so much for rails, but it was somewhat slow and washed out on jumps because it was so soft. Although you didn't mention it in your list of baords you were looking at, I'm currently riding a Capita Indoor Survival FK and I like it a lot more all around. It is a bit stiffer than the WWW so it handles speed and jumps a lot better and has more pop. It still performs nicely on rails too.