I am concerned that some here appear to be presenting Aspirin and Warfarin as interchangeable, potentially equal alternatives as prophylactic preventative treatments against strokes or heart attacks.
The drugs work differently, on different parts of the coagulation process, and are therefore both very useful for different types of conditions.It is therefore a mistake to present one as "better" than the other.
And both can have severe side effects,so neither should be taken as prophylaxis without medical consultation and monitoring, especially warfarin.
There has been a good study contrasting the efficacy of warfarin or aspirin in a very particular cohort of patients; in the treatment of patients who have suffered a heart failure but have a normal heartbeat. The conclusion to be drawn from the study would be as quoted on the NHS Choices website;
"These findings provide a good indication that warfarin and aspirin are both comparable as treatments, at least in people with heart failure, a normal heart rhythm and no apparent high risk of clots. The findings do not alter the current medical management of heart failure or clot-prevention, so it is likely that the choice between prescribing warfarin and aspirin will continue to be made on a case-by-case basis."
The study also had these major findings;
"Researchers found that there was no difference in the rate of clot-based strokes, bleeding in the brain or death in patients receiving aspirin compared with patients receiving warfarin."
and
"When strokes caused by clots (ischaemic strokes) were considered separately, warfarin was significantly better than aspirin at reducing the risk of stroke,"
http://www.nhs.uk/news/2012/05may/Pages/warfarin-aspirin-anti-bloodclot-trial.aspx
It would be wrong to present Aspirin and Warfarin as equal alternative treatments for all conditions, or to present one as "better" than the other.Both have value, used correctly.