Decanting is not tidiness, it is what makes dried food keep. A part-used bag of lentils rolled shut lets in air and moisture, and damp is what turns a cupboard staple into something that will not soften however long you boil it – the rehydration page explains why old beans sometimes never cook.
Square beats round by a wide margin in a van locker: round containers waste roughly a fifth of the space between them. Buy fewer, larger ones than you think, and check the seal rather than the marketing.