I don't disagree that the the legislative branch is (supposed to be) more representative, but reality is that their actions often get lost in the hubbub. Most people don't know what individual bills their own Representative or Senator vote for or against. A President, on the other hand, is a single person and much more high profile, and thus more prone to be mindful of what they do.
A President having line-item veto power would be really helpful with large bills and emergency relief bills where a lot of pork is hidden. For example, it's fine if Florida needs hurricane relief, but I don't want to see a fire station for Montana in a hurricane relief bill for Florida. They are not related. The fire station should stand on it's own. As it is now, that cannot be struck out without vetoing the entire relief bill, which would never be done due the the inevitable hue and cry that would result.