If you read what little literature is out there on the subject you will find that there is really no difference between ASA 325 and 81mg for stroke prevention. Most people start their patients on ASA 325 in the hospital just because they "think" it might be a little more effective even though there is no data to support this. Long term there is a slightly higher risk of bleeding complications on ASA 325, which is why most are eventually switched to 81mg. Most people just end up transitioning them to ASA 81mg at discharge.