Before revision:  This challenge stems from the enormous space of available solutions, with different sets of data instances and features that could be used for training, several algorithms to choose from, and instantiations of these algorithms  (i.e., models) that perform differently according to diverse metrics.
After revision:  This challenge stems from the enormous space of available solutions, with different sets of data instances and features that could be used for training, several algorithms to choose from, and instantiations of these algorithms (i.e., models) that perform differently according to various metrics.