How do I choose the best method to assess cell survival?

The considerations that should be taken into account for choosing the best method to assess cell survival include: timing, cell type, mechanism of cell death, and assay interpretation. Timing should be considered when choosing a toxicity or cell viability assay, as cell survival may rely on the duration of cells being treated. Additionally, some markers of cell death show at specific stages during apoptosis, such as PS translocation (which occurs in early apoptosis) or DNA fragmentation (which occurs late in apoptosis). 

Mechanism of cell death is another consideration that is important because cell viability and toxicity assays do not provide information into the mechanism of cell death during their experiments. Targeted experiments that utilize specific assays for cell death pathways (e.g. apoptosis) are required for showing the exact mechanisms of cell death.

Assay interpretation is another important consideration because experimental substances may not directly cause cell death, but instead change the cellular metabolism or cellular proliferation. This in turn can wrongly be interpreted as reduced viability. Thus, it's vital to use a combination of cell toxicity and cell viability assays to differentiate these possibilities.        

The cell types you are working with are also important considerations to make. For non-dividing cells or post-mitotic cells such as neurons, membrane or metabolic integrity assays are the ideal choice. The plating density and culture environment should ideally be standardized for best performance and for generating reproducibility in future experiments.