Final answer:
A competitive attack is more likely to produce a sustained competitive advantage under conditions of low resource similarity, as it engenders a situation where firms cannot easily copy each other's strategies.
Step-by-step explanation:
Under conditions of low resource similarity, a competitive attack by a rival is more likely to produce sustained competitive advantage. Low resource similarity implies that the firms in question do not share similar resources, be it technology, assets, competencies, or other strategic capabilities. This heterogeneity can make it more difficult for rivals to imitate or replicate a firm's strategies, thus allowing the initiating firm to maintain its competitive lead for a longer period.