Vacuum Energy: Cosmological Constant or Quintessence?

For a flat universe presently dominated by static or dynamic vacuum energy, cosmological constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed mass fraction as function of the present ratio of smooth energy to matter energy $\rat$. Identifying the normalized collapsed fraction as a conditional probability, we observe that the observed present ratio $\rat \sim 2$ is likely in LCDM, but more likely in QCDM. Inverse application of Bayes' Theorem implies that, in any fundamental theory, the prior for $\rat$ must be essentially flat over the allowed range. This is consistent with a generic class of fundamental theories of initial conditions that are practically indifferent to $\rat$. It does not demand the existence of potentially observable other universes.