I would prefer that people be able to just download a tarball,
extract it, and copy over a directory to the libs dir. And it just
works.
On the other hand, it can be very annoying for a user as well when
they already have a *newer* version of that same dependency
installed,
and then they install your library and suddenly things break.
That question is, What's the best way?
What are your target audience?
Developers/power-user would like control over what goes in.
Grandmas like everything to work with minimum hassel.
Tailor your solution (and it's robustness) to your audience.
My 2c.