There may exist no answer to this question.
An alternative could be to ask for methods to determine the two estimates efficiently for any problem at hand. The Bayesian methods are pretty close to this ideal. However, even though minimax methods could be used to determine the frequentist point estimate, in general, the application of the minimax method remains difficult, and tends not to be used in practice.
An other alternative would be to rephrase the question as to the conditions under which Bayesian and frequentist estimators provide “consistent” results and try to identify methods to efficiently calculate those estimators. Here "consistent" is taken to imply that Bayesian and frequentist estimators are derived from a common theory and that the same criterion of optimality is used for both estimators. This is very different from trying to oppose Bayesian and frequentist statistics, and may render the above question superfluous.
One possible approach is to aim, both for the frequentist case and the Bayesian case, at decision sets that minimize the loss for a given size, i.e., as proposed by
Schafer, Chad M, and Philip B Stark. "Constructing confidence regions of optimal expected size." Journal of the American Statistical Association 104.487 (2009): 1080-1089.
It turns out that this is possible - both for the frequentist and the Bayesian case - by including by preference observations and parameters with large pointwise mutual information. The decision sets will not be identical, since the question being asked is different:
- Independent of what is the true parameter, limit the risk of making wrong decisions (the frequentist view)
- Given some observations, limit the risk of including wrong parameters into the decision set (Bayesian view)
However the sets will overlap largely and become identical in some situations, if flat priors are used.
The idea is discussed in more detail together with an efficient impementation in
Bartels, Christian (2015): Generic and consistent confidence and credible regions. figshare.
https://doi.org/10.6084/m9.figshare.1528163
For informative priors, the decision sets deviate more (as is commonly known and was pointed out in the question and in answers above). However within the consistent framework, one obtains frequentist tests, that guarantee the desired frequentist coverage, but take into account prior knowledge.
Bartels, Christian (2017): Using prior knowledge in frequentist tests. figshare.
https://doi.org/10.6084/m9.figshare.4819597
The proposed methods still lack an efficient implementation of marginaization.