We show that a certain optimality property of the classical Bernstein
operator also holds, when suitably reinterpreted, for generalized Bernstein
operators on extended Chebyshev systems.
We complement a recent result of S. Furuichi, by showing that the differences
$\sum_{i=1}^n \alpha_i x_i - \prod_{i=1}^n x_i^{\alpha_i}$ associated to
distinct sequences of weights are comparable, with constants that depend on the
smallest and largest weights.