ASD more common in paradoxical embolism
If you get a question in USMLE and you have to choose between ASD and others (VSD, AV malformation, ...etc) then choose ASD.
The reason is that the pressure difference between the atria is less and so a thrombus can easily slip into the left side.
Typical USMLE case scenario would be a patient with DVT who developed stroke. What cardiac anomaly is expected? Answer: ASD.
Note that am not saying that VSD is wrong but they want you to be smart enough to realize that ASD is more likely.