Some buns prefer “tractor-supply hay” to Oxbow hay. You don’t know until you’ve tried though. Horse hay is fine for buns as long as it smells good. Hay must never smell the tiniest bit mouldy and it needs to have been stored in a dry place. If you can get hay from someone who keeps race horses you can be pretty sure it’s good quality, because race horses are very expensive and it’s not likely their owners would risk their health with poor quality hay. Hay for milk cows is good too, because the taste of the milk is affected by bad hay.
The reason why many of us choose Oxbow hay is mainly that they tend to have consistently high quality from batch to batch, and they’re a company that will respond to questions e-mailed to them. It feels safe to use.
As for cuts and types of hay, buns have their individual preferences. Some buns prefer crunchy, course hay, some prefer softer, leafier hay. Again, you don’t know what bun likes what hay until you’ve tried.