They are mostly not verified claims. Indeed these products behave in different ways, but for other reasons.
For example, easy rinsing does not depend on liquid or solid state, but on physical-chemical features of ingredients: the presence of cationic surfactants, the amount of sequestering agents (aimed at lowering water hardness and other things)… in particular, both liquid and powder products often contain substances – in the intention of the manufacturers – that must hold on clothes even after rinsing. We refer to optical brighteners, blue dyes and fragrances.
The “high amount” of water into liquid detergents may be a right statement: water is used to dissolve well all ingredients, but also to make the product easy to be dosed. Besides, generally powder detergents contain low amounts of water, but very high amounts of inert fillers, whose sole purpose is to… be bulky and voluminous. One of the most common fillers is sodium sulfate, able to cake insolubly into sewage pipes.
Finally, generally powder detergents wash better dusty soil and some kinds of stains (such as fruit), instead liquid detergents show to be stronger on greasy soil.
Bensos produces liquid and free from inert fillers laundry detergents; for fruity and other stains, we offer sodium percarbonate, a powder additive. Every Bensos’ products are free from optical brighteners and blue dyes, almost all are free from fragrances; the perfumed ones contain neither allergens nor phtalates.