I've used Darren Hiebert’s Exuberant-ctags for a quite a while; it is an essential part of my vim toolbox. I tag python, Java and C code (I also use cscope).
Recently, I've read that I should be considering moving to a more modern fork of it called Universal-ctags.
I'm looking for specific technical pros and cons to making such a move: do the tags change? what new features, if any, can/should I employ? are there any gotchas I need to be aware of?
Regarding C++, it makes the difference -- I can't tell regarding C or Java. It has a better understanding of C++ code bases than exuberant ctags.
Otherwise, it's maintained, with unit tests. If it was a fork of an active project, well I may not be able to sort the two. In this case, it's a fork of an unmaintained project. It's built upon what ex-ctags had to offer to offer, let's hope, more.