In this study, predictions obtained in the four and in the five
flavour schemes are compared for two important processes involving heavy
flavours at the LHC: the production of a Z or a Higgs boson in association
with b quarks. In particular we obtain predictions with \Sherpa's
\MCatNLO implementation for the four--flavour scheme, treating the b's
as massive, and with multijet merging at leading and next-to leading
order for the five--flavour scheme.
While differences between the two schemes, at the inclusive level,
are well understood from resummation of possibly large logs into
the b-PDFs, differences in shape present a major problem
for experimental measurements. We make use of data for Z+b(ˉb)
production at the 7 TeV LHC to exhibit strengths and weaknesses of the
different approaches and we use these results to validate predictions for
b-associated Higgs-boson production at the 13 TeV Run II.