Neither. While both drugs lower cholesterol (which is a surrogate end point for preventing heart disease), neither drug has been shown to actually prevent heart disease. Statins (like crestor, lipitor, (atorvastatin) and zocor) have, by far, the best proven track record for secondary and primary prevention of heart disease. For people with side effects, very tiny doses are usually well tolerated and probably effective.
Both Have Merit. Both Zetia (ezetimibe) and welchol work to decrease cholesterol absorption from the gut. The effect is an increase in LDL receptors that result in reducing circulating LDL particles. Welchol has the added effect of reducing blood hemoglobin a1c levels, the measure of glucose levels over a 3 month period, by 0.5 mg%. Rarely are these agents used 1st line. Rather, they are added to statins where appropriate.
Depends. Depends what works for you (you are a unique individual). Speak to your physician.