  Variability classes in the enigmatic black hole candidate GRS 1915+105 are
known to be correlated with the variation of the Comptonizing Efficiency (CE)
which is defined to be the ratio between the number of power-law (hard) photons
and seed (soft) photons injected into the Compton cloud. Similarities of light
curves of several variability classes of GRS 1915+105 and IGR 17091-3624, some
of which are already reported in the literature, motivated us to compute CE for
IGR 17091-3624 as well. We find that they are similar to what were reported
earlier for GRS 1915+105, even though masses of these objects could be
different. The reason is that the both the sizes of the sources of the seed
photons and of the Comptonizing corona scale in the same way as the mass of the
black hole. This indicates that characterization of variability classes based
on CE is likely to be black hole mass independent, in general.
