  We have analyzed in a systematic way about nine years of INTEGRAL data
(17-100 keV) focusing on Supergiant Fast X-ray Transients (SFXTs) and three
classical High Mass X-ray Binaries (HMXBs). Our approach has been twofold:
image based analysis, sampled over a ~ks time frame to investigate the
long-term properties of the sources, and lightcurve based analysis, sampled
over a 100s time frame to seize the fast variability of each source during its
~ks activity. We find that while the prototypical SFXTs (IGR J17544-2619, XTE
J1739-302 and SAX J1818.6-1703) are among the sources with the lowest ~ks based
duty cycle ($<$1% activity over nine years of data), when studied at the 100s
level, they are the ones with the highest detection percentage, meaning that,
when active, they tend to have many bright short-term flares with respect to
the other SFXTs. To investigate in a coherent and self consistent way all the
available results within a physical scenario, we have extracted cumulative
luminosity distributions for all the sources of the sample. The
characterization of such distributions in hard X-rays, presented for the first
time in this work for the SFXTs, shows that a power-law model is a plausible
representation for SFXTs, while it can only reproduce the very high luminosity
tail of the classical HMXBs, and even then, with a significantly steeper
power-law slope with respect to SFXTs. The physical implications of these
results within the frame of accretion in wind-fed systems are discussed.
