Tc-99m has multiple oxidation states, therefore it can bind with many organic molecules such as glucoheptonates, phosphonates etc. Thus it can be used for many different types of diagnostic imaging. It releases low-energy gamma radiation, thus does not pose any radiation risk to healthy tissues.
Co-60 has a half life of 5.27 years and thus can remain in irradiation facilities for long periods without the need for replacement. It releases high-energy gamma radiation upon radioactive decay, thus killing pathogens such as bacteria and fungi - hence extending the shelf life of irradiated foods such as strawberries, potatoes and frozen foods.