I think NM_CACHED_QUARK_FCN() is better because:
- the implementation is in our hand, meaning it is clear that
putting a "static" before NM_CACHED_QUARK_FCN() is guaranteed to
work -- without relying on G_DEFINE_QUARK() to be defined in a way
that this works (in fact, we currently never do that and instead
make all functions non-static).
- it does not construct function names by appending "_quark".
Thus you can grep for the entire function name and finding
the place where it is implemented.
- same with the stings, where the new macro doesn't stringify the
argument, which is less surpising. Again, now you can grep
for the string including the double quoting.
(yes, I really use grep to understand the source-code)