It all depends on what you are going to do with it. Mine is used half for business and half for recreation. The 4.6L has more power for loads and seems to get better gas mileage too by a little....but not under all conditions...This is just my comparison with guys I know who use them for construction and long commutes to the sites. The 5.4L is good if you tow heavy stuff all the time but they eat gas heavily.