So I just brought the Horse armor DLC on xbox 360 and I'm just wondering if it affects how fast the horse runs? If the horse has armor would it be slower or faster?

I thought I heard a lot about the horse armor being crap. But then again I hardly know anything about TES

I think it keeps the speed the same, it only makes the health value higher, instead of adding an Armor rating.

The heavy armour slows you down more but is stronger and the elven armour slows you down a bit but offers less protection.

And since you are on the console - do not put armor on shadowmere as it breaks her AI packages and she will not return to her home if you lose track of her !