A relative has sent me five GEDCOM files of different family branches. They are partly redundant, their content is formatted differently and place names are inconsistent. While most programs offer merging functionality, including Gramps and MacFamilyTree which I tried here, this functionality is often limited and requires a lot of manual work (choosing entries to merge). I also found GenMerge, this tool seems sophisticated but only runs on Windows computers (I am on a Mac).
What alternatives are there for merging complete family trees? Is there an online service for this task? What is the tool of your choice and why?