The specialization of the configuration space of a software system has been considered for targeting specific configuration profiles, usages, deployment scenarios, or hardware settings. The challenge is to find constraints among options' values that only retain configurations meeting a performance objective. Since the exponential nature of configurable systems makes a manual specialization unpractical, several approaches have considered its automation using machine learning, i.e., measuring a sample of configurations and then learning what options' values should be constrained. Even focusing on learning techniques based on decision trees for their built-in explainability, there is still a wide range of possible approaches that need to be evaluated, i.e., how accurate is the specialization with regards to sampling size, performance thresholds, and kinds of configurable systems. In this paper, we compare six learning techniques: three variants of decision trees (including a novel algorithm) with and without the use of model-based feature selection. We first perform a study on 8 configurable systems considered in previous related works and show that the accuracy reaches more than 90% and that feature selection can improve the results in the majority of cases. We then perform a study on the Linux kernel and show that these techniques performs as well as on the other systems. Overall, our results show that there is no one-size-fits-all learning variant (though high accuracy can be achieved): we present guidelines and discuss tradeoffs. CCS CONCEPTS • Software and its engineering → Software product lines; • Computing methodologies → Classification and regression trees.