Why are sword units less effective than spear units in the game? The answer just may be the truth.
It seems what we know about Samurai is mostly from a later period, but in the Sengoku (15th to begining of the 17th centurys) the weapons of choice were the Yumi, then Yari, and then the Teppo. Enjoy!

The Soul of the Samurai?
Misconceptions of the Japanese Sword

By A. Knowles

The Japanese sword has acquired mystical significance in the wake of Samurai history, but to what extent is this image justified? This article will attempt to shatter a few myths surrounding both the use and omnipotence of the sword in the samurai arsenal. Tokugawa Ieyasu's famous remark that the sword was the 'soul of the samurai' should not be taken at face value. This was most likely a comment made reflecting the relatively peaceful years of Sekigahara (1600) to Osaka (1614) when battlefield weapons (i.e. firearms, spears and bows) were being pushed to the back of samurai life and the sword as the weapon of everyday life.
Read the continuation at:

http://www.samurai-archives.com/sts.html