[clarete]

First things that come to my mind:

s3cmd: * might be considered more robust and battle tested as people already commented here; * is written in python, so if you have a python environment running, you might be more comfortable with it;

s3sync * Smaller codebase, might be easier to keep things simpler and well tested, achieving the same stability with less time/effort; * Error reporting. One of my main reasons to keep working on s3sync was its better error reporting. I just go crazy when something wrong happens and I don't know why. * It's in ruby, if you have a ruby environment and you don't want to add any python dependencies, you might choose it