Non-canonical inflection (suppletion, deponency, heteroclisis...) is extensively studied in theoretical approaches to morphology. However, these studies often lack practical implementations associated with large-scale lexica. Yet these are precisely the requirements for objective comparative studies on the complexity of morphological descriptions. We show how a model of inflectional morphology which can rep- resent many non-canonical phenomena (Walther, 2011), as well as a formalisation and an implementation thereof can be used to evaluate the complexity of competing morphological descriptions. After illustrating the properties of the model with data about French, Latin, Italian, Persian and Sorani Kurdish verbs and about noun classes from Croatian and Slovak we expose experiments conducted on the complexity of four competing descriptions of French verbal inflection. The complexity is evaluated using the information-theoretic concept of description length. We show that the new concepts introduced in the model by Walther (2011) enable reducing the complexity of morphological descriptions w.r.t. both traditional or more recent models.