Evidence is accumulating supporting a better effect from DHA over EPA. DHA is more effective at lowering blood pressure and improving endothelial function. It is more effective for raising HDL and decreasing platelet adhesion and aggregation. Both EPA and DHA decrease fasting TG by approximately 14-35% depending on the TG levels and dose of EPA/DHA used. DHA is more effective for altering lipoprotein size because it is a more potent inhibitor of cholesterol ester transfer protein (CETP) activity, an enzyme involved in lipoprotein particle size. In animal and human studies, DHA was more effective than EPA in reducing both systolic and diastolic blood pressure. DHA was also shown to be able to lower heart rate whereas EPA was not able to do this.
So look for fish oil products that have more DHA than EPA to gain the most cardiovascular benefits.