I'd choose the MillHorse before the Poser horse directly! I've even gone through the trouble and extra work to exchange all images (hundreds of them) in our project just to have the new horse instead.

One can go far with tweaking the dials creating different breeds. But the built in breeds aren't that great.

Daz3D is working on a service release which is due as soon as it looks ok after our wishes. See wishlist at DAZ3D.

Movida has done a "backfix" morph and an Arabian head morph. Available in freebies here.