Around 500 years ago, when our school Muso Shinden Eishin Ryu Iai Heiho (MSERIH) was created by Hayashizaki Jinsuke, the swords used were longer than what many schools use today. By the time of the 7th headmaster, Hasegawa Chikaranosuke Eishin, the swords used by samurai became shorter. However, our school today still uses the original sword lengths. The lengths are relative to an individual's height.
Some of the benefits of using a longer heavier sword is that it helps to better develop the seika tandem (generating power from the centre of mass) and relaxation, skills warriors needed to endure many tiring hours on a battlefield.
This picture above shows an iaitou sword 3.0 shaku long used in MSERIH by someone approximately 185cm/6ft tall compared to a typical 2.45 shaku sword that would be used in many other styles by a person of the same height.