Helmets are designed for specific uses. Bicyclists encounter different head trauma than horse riders because it's a different activity. (biker riders tend to hit the front of their head while we horsey folk tend to bash the back of our heads!) Helmet manufacturers take this into consideration thus the different helmet types.
That being said I like Troxel and have had several of them. Lightweight, comfy, and they do the job. A review on Troxel helmets can be found HERE.