Board Thread:Questions and Answers/@comment-10797017-20130622101437/@comment-24282510-20140606161137

Gacsam wrote: It most likely has to do with their body type and their style of fighting, for example Suì-Fēng is very fast, and Suzumebachi is a weapon for quick and precise strikes.

That is pretty much stated servel times in the series when they say a zanpakuto is based off of the owners soul.