Whether mass marketing is 'better' than niche marketing depends on the firm and its market. Both are valid strategies with opposite strengths, so the claim that one is always better is unlikely to hold.
The case that mass marketing is better. Mass marketing reaches the whole market, so it offers the largest potential sales and revenue. Producing in huge volumes brings economies of scale, lowering unit costs so the firm can price competitively and still profit β a self-reinforcing advantage that small niche firms cannot match. Demand is spread across many buyers, so the firm is not dependent on one small group, reducing the risk of sudden collapse. For a large, well-financed firm in a market with broadly similar needs, mass marketing can clearly be the superior strategy.
The case that niche marketing can be better. For a small firm or start-up, niche marketing is often the only realistic option, because it cannot afford the large factories, wide distribution and heavy advertising mass marketing demands. A niche offers less competition, higher margins and loyal customers, which can make a small firm more profitable per unit than if it tried (and failed) to compete in a crowded mass market. Niche marketing also suits markets where customers have distinct needs that a single standardised product cannot satisfy. In these cases niche marketing is plainly better for the firm concerned.
Weighing it up (criterion). The better strategy depends on the firm's size and resources and the nature of the market. Mass marketing tends to be better for a large, well-financed firm serving an undifferentiated market, where scale and reach dominate. Niche marketing tends to be better for a small firm, or where customers have specialised needs, where focus and margin matter more than volume. Each strategy also carries a distinctive risk β price wars and inflexibility for mass, small size and vulnerability for niche.
Judgement. Mass marketing is not always better than niche marketing. It is usually the stronger strategy for a large firm with the finance to exploit economies of scale in a market of similar needs; but for a small firm, or in a market of specialised needs, niche marketing is frequently the better β and sometimes the only viable β choice. The most defensible conclusion is that neither strategy is universally superior: the right choice is the one that matches the firm's resources and the market it serves, so 'better' can only be judged case by case.