The following is primarily from a FFPE point of view
1. Is the antibody interpretable and will it help in your research/diagnostics? In other words, is it robust and reproducible and does it localise to an appropriate cell type or compartment of interest and to a particular subcellular compartment?
2. Is there an automated platform? I would recommend automated platforms (cf bench workup) antibodies whenever possible ahead of cost considerations as reproducibility is increased and the time to optimisation should be decreased.
3. Is the well published clone suitable for your needs and are there established interpretations of expression? Deciding upon correct thresholds can be extremely time consuming and require appropriate justification.