Every time we develop a Drupal site, we have time to compare pros and cons, similarity and differences of modules before we use in the projects. Drupal community is really awesome. The community created "Comparisons or Drupal modules" in various places of D.O. Sometimes they are hard to find and spread else where. Sometimes comparisons are coming outside of D.O.
I have compile the "Comparisons or Drupal modules" in this list. Now I can use the list for new & existing projects.
I hope this also can really save time too. Enjoy and save your research time. This list will be growing and changing, still tune with it.