Just my preference, though the larger variety of tube options for the Woo and my finding a combination I like probably has more to do with it than the differences in topology. Wanted to find something that took the edge of the PS1Ks a bit.
You see, I don't find that they are edgy, but I do feel they can sound more alive…don't get me wrong at all about the WA6, I love it, but I may feel the PS's would benefit from the current, I don't know.