 The latter (referred to as "la-based minor") is sometimes preferred in choral singing, especially with children.The choice of which system is used for minor makes a difference as to how you handle modulations.In the first case ("do-based minor"), when the key moves for example from C major to C minor the syllable do keeps pointing to the same note, namely C, (there's no "mutation" of do's note), but when the key shifts from C major to A minor (or A major), the scale is transposed from do = C to do = A.