It is said to have more nutritional value. I used to feed it in Germany because it was easy to find in roundbales straight from the producer.
I also fed the small square bales. It takes some getting used to the smell, tho. Horses love it!
BUT....it needs to be stored right, covered well, so the plastic wrapping doesn't get punctured by birds or the hunting kittie. Once air enters it spoils very rapidly. Means big round bales only when there are several horses who consume a bale in about 4 days. Same for the small bales. The botulism risk is there, sometimes a dead mouse accidently baled in is enough.
It takes a lot of watching when feeding it. Any damaged wrapping or little hole, and that bale is unsafe.
I stay away from it. Unless I have a COPD horse. Im worrying enough as it is. Don't need the extra excitement