  We introduce an operational and statistically meaningful measure, the quantum
tomographic transfer function, that possesses important physical invariance
properties for judging whether a given informationally complete quantum
measurement performs better tomographically in quantum-state estimation
relative to other informationally complete measurements. This function is
independent of the unknown true state of the quantum source, and is directly
related to the average optimal tomographic accuracy of an unbiased state
estimator for the measurement in the limit of many sampling events. For the
experimentally-appealing minimally complete measurements, the transfer function
is an extremely simple formula. We also give an explicit expression for this
transfer function in terms of an ordered expansion that is readily computable
and illustrate its usage with numerical simulations, and its consistency with
some known results.
