Before I got mine the P1i, I also have a choice to try W960. Few reasons why I opt for P1i:-

They have same OS with P1i, W960 got built in more giga memory 8gb and but I dun need that. My 1gb hardly reach 1/4 of total usages.
Walkman 3.0 can be mod easily into my P1i.
P1i has more executive look (as what some poster said before).
P1i is cheaper of course with the same performance equals to W960.

Just my opinion worth of coin.