The convergence behavior of QMR
is typically much smoother than for BiCG.
Freund and Nachtigal [102] present quite general error
bounds which show that
QMR may be expected to converge about as fast as GMRES. From a relation
between the residuals in BiCG and QMR
(Freund and Nachtigal [relation (5.10)]FrNa:qmr) one may deduce
that at phases in the
iteration process where BiCG makes significant progress, QMR has arrived
at about the same approximation for 
.
On the other hand, when BiCG makes
no progress at all , QMR may still show slow convergence.
The look-ahead steps in the version of the QMR method discussed in [102] prevents breakdown in all cases but the so-called ``incurable breakdown'', where no practical number of look-ahead steps would yield a next iterate.