Cyborg horse would be a happy medium. I know that XM is great at doing armors/mechanical parts. They are also good at most things
I voted real horse. But that's not to say don't armor up the horse. I just don't get the logic of the robot horse. Seems like they are doing it just to do it. If robots were the theme through the line, I would get it. But so far, the most "mechanics" we have seen are Bane's juice pack and Catwoman's motorcycle. Just a basic, slightly more streamline motorcycle.
Joker, Batman, Harley, Poison Ivy, Batgirl -- none of these have any hints of machines. It's not like they are even fighting machines/robots.
If XM wants to do a robot horse, I can see it fitting into the Batman Wasteland line more. Think about it.....horses wouldn't be able to stand the radioactivity, so Batman made one.