BOSS's "WAZA CRAFT" series is a premium line where skilled Japanese engineers meticulously brush up standard models, from circuit design and part selection to manufacturing. The main differences are the use of carefully selected discrete circuits and parts, improvements in noise and sound quality, and the inclusion of a mode switch on many models that allows you to switch between the "original sound" and the "modified (Waza) sound." As for whether you need to buy one, it is not strictly necessary if you are satisfied with the original tone, but it is a very valuable option for those seeking higher sound quality and better cut-through, or those who want to switch between vintage sound and modern custom sound with a single unit.