how do I know which is best to use for simple/complex logging on files?

That's not a simple question, and a question CPAN will never even attempt to answer. CPAN is just a medium. It allows anyone to upload anything, and to download anything. It tries to index things as best as it can, but it doesn't judge. Any module is as equal as the other. It doesn't have a fad-of-the-week. It doesn't favour incrowd over newbies. It doesn't tell you what you should use.

As for your question, what is "best" depends on what you think it good in a module. Do you rank speed over ease of use? Do you prefer objects over a procedural interface? And when is logging simple or complex anyway? Considering those answers will vary from person to person, it would be very hard for someone to say "you should module X" - assuming you want that someone to have your best interest in mind. Not to mention said someone should reevaluate which module is best each time a new logging module hits CPAN.