  The historic first joint detection of both gravitational wave and
electromagnetic emission from a binary neutron star merger cemented the
association between short gamma-ray bursts (SGRBs) and compact object mergers,
as well as providing a well sampled multi-wavelength light curve of a
radioactive kilonova (KN) for the first time. Here we compare the optical and
near-infrared light curves of this KN, AT2017gfo, to the counterparts of a
sample of nearby (z < 0.5) SGRBs to characterize their diversity in terms of
their brightness distribution. Although at similar epochs AT2017gfo appears
fainter than every SGRB-associated KN claimed so far, we find three bursts
(GRBs 050509B, 061201 and 080905A) where, if the reported redshifts are
correct, deep upper limits rule out the presence of a KN similar to AT2017gfo
by several magnitudes. Combined with the properties of previously claimed KNe
in SGRBs this suggests considerable diversity in the properties of KN drawn
from compact object mergers, despite the similar physical conditions that are
expected in many NS-NS mergers. We find that observer angle alone is not able
to explain this diversity, which is likely a product of the merger type (NS-NS
versus NS-BH) and the detailed properties of the binary (mass ratio, spins
etc). Ultimately disentangling these properties should be possible through
observations of SGRBs and gravitational wave sources, providing direct
measurements of heavy element enrichment throughout the Universe.
