Software libraries ease development tasks by allowing client developers to reuse code written by third parties. To perform a specific task, there is usually a large number of libraries that offer the desired functionality. Unfortunately, selecting the appropriate library to use is not straightforward since developers are often unaware of the advantages and disadvantages of each library, and may also care about different characteristics in different situations. In this paper, we introduce the idea of using software metrics to help developers choose the libraries most suited to their needs. We propose creating library comparisons based on several metrics extracted from multiple sources such as software repositories, issue tracking systems, and Q&A websites. By consolidating all of this information in a single website, we enable developers to make informed decisions by comparing metric data belonging to libraries from several domains. Additionally, we will use this website to survey developers about which metrics are the most valuable to them, helping us answer the broader question of what determines library quality. In this short paper, we describe the metrics we propose in our work and present preliminary results, as well as faced challenges.