One way to evaluate the question is to look at the dynamics of how different sized bodies operate, and then to decide, on whatever criteria one would like, what is best.
Generally speaking, the larger the deliberative body, the most power ends up vesting in the leadership group, and the less power ends up in rank and file members. For example, in the U.S. House of Representatives, the House leadership, the committee chairs and the Rules committee control proceedings tightly, and members of the minority and members of the majority's rank and file have very little power.
Similarly, in the U.K.'s very large House of Commons, almost all power is vested in the cabinet chosen from senior members of the majority party, while "backbenchers" attend to minor, almost clerical details of legislative drafting and participate now and then in debate on the floor when they have the opportunity to do so. But, most individual MPs have little power. The Speaker's power to control debate, which is necessary, further limits the power of rank and file members.
But, in a large body, it is far less likely that everyone will overlook any key detail of legislation, because even subcommittees are quite large and have relatively modest amounts of legislation to consider relative to the number of legislators charged with reviewing it.
In contrast, in a smaller deliberative body, such as Colorado's state senate with 35 members, almost every member of the majority holds some committee chairmanship or leadership post affording that member considerable power in some particular subject matter area, committees are relativity small affording every member of any committee considerable power, and the cost of even a small number of defections from a bill that the party supports makes catering to each individual member's wishes critical for management of the body. Members all know each other on a face to face basis and the interpersonal relationships can sometimes reduce partisanship and make for relatively expeditious consideration of legislation even at a fairly deliberative pace. Most floor debate can proceed with only perfunctory attention to formal rules of procedure.
As numbers growth, the character of the body goes from one extreme to the other.