Recent trends in Positron Emission Tomography (PET) use the time-of-flight (ToF) information in the image reconstruction process to improve the signal-to-noise ratio and the positioning of the annihilation event. One of the components that most contributes to the accuracy of the ToF-PET is the scintillation crystal. The metascintillator approach has been proposed to overcome the time resolution limits of commonly used scintillators. The metascintillator is an engineered composition of small units that combines and optimizes several features in a single scintillator heterostructure. In this work, metascintillator-based brain PET systems were modeled using the GATE Monte Carlo toolkit and compared with designs based on bulk LYSO or BGO. Sensitivity, noise equivalent count rate and scatter fraction were evaluated following the NEMA guidelines. Only data in the list mode format was used for comparison purposes to avoid dependence on the image reconstruction algorithm. To achieve the same peak sensitivity of a system based on a 15 mm thick bulk BGO, the metascintillator-based scanners using BGO/BaF2 , BGO/EJ232, LYSO/BaF2 and LYSO/EJ232 must have thicknesses of 23.2 mm, 22.5 mm, 29.7 mm and 31.1 mm, respectively. The objective of this work is to determine the clinical value of using metascintillator-based detectors in brain PET.