What are the significant differences between the Sharethis, Addthis, and Service Links modules? AddThis
Service Links
ShareThis


These three modules appear to be very similar in terms of functionality.  AddThis has about double the number of the installs compared to the other two, but Service Links and ShareThis each have over 10,000 installs, which is not too shabby.

What, if any, are the significant differences among these modules?
There is some detailed information on each of these, and others, over at Comparison of Social Network connectors/Sharing modules.  It would be best to add any new information to that wiki page so that we have something that's always up-to-date.