Theory choice decisions were at the focus of the debate on theory change that dominated the philosophy of science in the 1960's and 1970's. Comparative evaluations of competing theoretical approaches were supposed to form the nucleus of scientific progress and, at the same time, the nucleus of scientific rationality. A theory choice decision singles out the methodologically most qualified alternative from among a set of rival theories. A sequence of such decisions is supposed to generate a series of theories with increasing methodological virtue; and a series of this kind constitutes scientific progress. Moreover, scientific rationality is tied to the nature and justification of the criteria brought to bear on theory choice decisions. Rational theory choices are made relying on objective and epistemically significant criteria. The intertwinement of rationality, theory change and theory choice is among the outstanding commitments underlying the entire debate on "theory dynamics"; in particular, it is constitutive of the methodological approaches of Larry Laudan and, above all, Imre Lakatos. The backdrop, against which this debate unfolded, is provided by the methodological challenge involved in Thomas Kuhn's philosophy of science. My objective is to elucidate more clearly Lakatos' attempt to neutralize methodological threats he assumed to be inherent in some of Kuhn's claims on theory change.