A fair comparison of multiple live cell cultures requires examining them under identical environmental conditions, which can only be done accurately if all cells are prepared simultaneously and studied at the same time and place. This contribution introduces a multiplexed lensless digital holographic microscopy system (MLS), enabling synchronous, label-free, quantitative observation of multiple live cell cultures with single-cell precision. The innovation of this setup lies in its ability to robustly compare the behaviour, i.e., migratory pathways, of cells cultured or contained in different ways (with varied stimuli applied), making it a valuable tool for dynamic biomedical diagnostics on a cellular level. The system's design allows for potential expansion to accommodate as many samples as needed, thus broadening its application scope in future quantitative diagnostics on global multi-culture cellular behaviours via their localized single-cell spatiotemporal optical signatures. We believe that our method has the potential to empower reliable live cell multi-culture comparisons through simultaneous quantitative imaging, enhancing label-free investigations into cell cultures and the effects of biochemical or physical stimuli over large areas, and unlocking novel mechanistic understandings through high-throughput time-lapse observations.