If you are cooking them, the rolled/crimped ones would cook faster/easier, but can't image the end result would be much different. You might want to check out the fermenting feeds thread, they have talked about using both over there. Some people feed horses the oats crimped or rolled etc because they are more digestible for them, think around 10% is the number you usually see. For feeding older chickens don't remember seeing that it makes much difference since they have a different digestive system with the crop/gizzard. Some birds do like the oats rolled/crimped better than whole and eat them more enthusiastically. The only thing I can really think of that would make a difference is cleaned/ good quality oats have a lot less hull and garbage in there, and rolled/crimped oats are usually cleaned.
