Consider the duplicate code. In particular, consider the number of functions and their length. If both plugins share only a couple formatting methods, it's not such a big deal to duplicate that code in order to keep the plugins self-contained.
If the duplicate code is getting pretty hefty, start thinking about doing one of the following:
Merge the plugins into a single plugin. Only do this if the two plugins fit into the same problem space. Take a good hard look at the plugins. There's a chance that what made them seem separate before was illusory and the fundamental behaviors are closely related.
Extract the duplicate code into a third plugin which is a dependency of each of the plugins that share the code. Only do this if the duplicate code is related and make sense as a plugin.