Perlite for drainage. If you are using a peat based mix you do not need the extra moisture retention of vermiculite. This is assuming you are talking about indoor container growing.
Most outdoor soil though usually can benefit from the use of both of them.
for drainage and aeration, perlite > vermiculite; but some other options are good too: pumice and rice hulls come immediately to mind since they won't float up and out of your mix like perlite may.
be easy,