  In this paper we argue that having available higher order fully exclusive
Monte Carlo generator for Higgs boson production from heavy quark fusion will
be mandatory for data analysis at LHC. The H to tau tau channel, a key for
early discovery of the Higgs boson in the MSSM scenario, is discussed. With
simplified example and for mH = 120 GeV we show, that depending on choice among
presently available approaches, used for simulation of Higgs boson production
from b bbar H Yukawa coupling, final acceptance for the signal events being
reconstructed inside mass window may differ by a factor of 3. The spread is
even larger (up to a factor of 10) for other production mechanisms (promising
for some regions of the MSSM parameter space). The complete analysis, which
necessarily will add stringent requirements for background rejection (such as
identification of b-jet or veto on b-jet) and which will require statistical
combination of samples selected with different selection criteria may only
enhance the uncertainty.
