another thing that some people might take into account when considering advantages/disadvantages, is that de-ionized, distilled or any further purified water will have more ecological footprint than your tap water (energy/material costs for the purification, packaging and transport). For me the fact that its more expensive, doesnt really change anything in terms of yields or purity and has more ecological impact makes me feel its unnecessary, but I can only talk about myself, each one will have their own motives.