Doesn't matter whether it's dynamic or not, if there's a log of hair it will render slowly.  Try rendering the fuzzy version of the bedtime sets plush bear.  Look at it this way to get really nice looking hair you need to have about 14,000 - 20,000 hairs.  Much more than that and Poser will choke.  Each hair casts a shadow.  I think you get where I'm going with this.