In the Senate, there is the provision for filibuster, and if left unturned, can prevent a vote, and if the bill runs out of time, can be killed. It is very easy for a President to veto legislation that has been passes by Congress, and it is very difficult to overturn such a veto. When the Legislative is separated from the Executive, there are two different agendas, and this fragmentation usually leads to a inconsistent, confrontational legislative process. Anderson noted this when he observed the conflict between Congress and Nixon, especially during his second term. The President's line item veto can also take the substance out of legislation.
Congressional procedures do have their advantages however.
There are those who argue that the lengthy process makes sure that all legislation is well debated, analysed, and considered, to ensure that the final product is a sensible program. Committee members are usually experts in their field, and their opinion in ironing out the problems in bills can be invaluable. The Conference Committee can produce a final product that contains elements from both houses, and can be considered objective. This view however, is highly idealistic, but unrealistic. Congressmen may not that objective, or indeed, that ethical.