Comparing the fits of the different enzyme inhibition models requires thinking both about enzyme mechanism and about statistics. Some notes:
•The mixed model generalizes competitive, noncompetitive and uncompetitive. Each of those three models are special cases of the mixed-model.
•Comparing R2 is an easy way to compare fits, but not a very good method.
•Comparing the adjusted R2 is a better way to compare fits. To do this, you need to ask for reporting of adjusted R2 in the parameters dialog. But this is not a rigorous way to compare models.
•Prism can compare models using two rigorous approaches, the extra sum-of-squares F test and the AICc approach.