From the standpoint of fundamental physics, black holes with
the same spin parameter are the same regardless of their mass.
Astrophysically, however, the environments of black holes do
depend on their mass, hence so do the properties of mergers
between black holes. I will discuss the likely properties
of mergers as a function of mass, with particular emphasis on
eccentricities and spins. I will also present several currently
open questions about the astrophysics of black hole coalescence.