The people who wrote the Constitution wanted the House of Representatives and the Senate to be rather different. They wanted the House to be more of a populist body while the Senate was to be a more deliberative and elite body. This has helped to shape the respective strengths and weaknesses of these two houses.
The House’s main strength is that it has an easier time getting things done. The individual members of the House have much less power than the individual members of the Senate do. Therefore, the House can pass legislation much more easily than the Senate. The major weakness that goes along with this is that the House is somewhat less democratic. Its majority party has the ability to push things through without support from the minority at all.
The Senate has the opposite strengths and weaknesses. Its major weakness is that it is very easy for a minority of Senators to block legislation. This means that the Senate can be the cause of a great deal of gridlock. The strength of the Senate is that its rules promote consensus and a greater level of democracy.
The strengths and weaknesses of the House of Representatives represent the flip sides of the same coin. For the majority party, the House's rules are great; for the minority party, those same rules condemn it to perpetual impotence with respect to the legislative process. The House of Representatives functions under a strict set of rules that strongly favor the majority party. The majority sets the agenda, controls all Floor proceedings, and controls the committee structure. While the minority can compensate for its impotence through the careful negotiation of arrangements with sympathetic members of the majority, such instances are generally limited to parochial matters involving federal spending for projects important to a particular state or region. An exception to that practice was the tendency of so-called "Blue Dog" Democrats -- fiscally conservative but socially liberal Democrats -- to side with Republicans on fiscal matters like tax and monetary policies.
Another strength of the House of Representatives lies in its constitutional authority to originate spending bills. Article I, Section VII of the Constitution states: "All Bills for raising Revenue shall originate in the House of Representatives; but the Senate may propose or concur with Amendments as on other Bills." In short, the most important authority of Congress, its control of the government's purse, cannot be exercised unless or until the House acts.
A weakness of the House is its size. Its 435 members make it unwieldy and difficult to manage relative to the much smaller Senate. Important House committees, like Transportation and Infrastructure and Armed Services can include sixty to seventy members -- an absurd number for an individual committee and one driven primarily by parochial considerations.
The Senate functions very differently from the House. For starters, as noted, there are far fewer members of the Senate than the House (100 to the House's 435). More significantly, the rules of the Senate allow for an inordinate amount of power on the part of each senator. Unlike the House, a single senator can hold up legislation or nominations on important positions like secretaries of federal agencies and ambassadors to foreign countries. Similarly, the Senate's authority to ratify treaties allows for the process to be derailed by a single senator who may not object to the treaty in question but who is using the treaty's importance to try to leverage the White House or the Senate's leadership on an unrelated matter. Among the most important strengths of the Senate is its role in the process by which presidential nominees to the U.S. Supreme Court are confirmed or rejected. The president's authority to nominate individuals to serve on the Supreme Court is among his or her most important and far reaching. The Senate's role in confirming those nominations, then, is equally important.
As noted, the Senate's greatest weakness is the disproportionate strength a single senator wields relative to his or her miniscule percentage of the body. Only one of the 100 senators is all it takes to slow down or stop the wheels of government from turning. The filibuster rule allows any senator to speak on the floor of the Senate as long as he or she can physically do so, which means any individual senator can hold up proceedings as long as he or she can continue speaking on the Senate floor.