The convergence behavior of QMR is typically much smoother than for BiCG. Freund and Nachtigal  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  prevents breakdown in all cases but the so-called ``incurable breakdown'', where no practical number of look-ahead steps would yield a next iterate.