I/O and RBV are both interested in competitive advantage. However, their views on what competitive advantage is and on what it is based differ. Whereas I/O reasons that environmental pressure and the
ability to respond to it are the prime determinants of firm success, RBV states that idiosyncratic and firm-specific sets of imperfectly mobile resources determine which firm will reach above-normal performance (Wernerfelt, 1984; Dierickx and Cool, 1989; Barney, 1991; Peteraf, 1993). RBV emphasises the characteristics of the underlying factors behind low-cost and differentiation and the value chain, that is, the resources of the company. A key RBV attribute is resource rareness, but a valuable, rare resource also needs to be costly to imitate or to substitute to sustain the advantage of the resource. RBV occupies a more prominent role in strategy today than I/O, but RBV too has limitations. Critics put focus on the lack of empirical studies, the relative lack of process orientation, and shortcomings in explaining hypercompetitive industries (Hedman and Kalling, 2003).