AF-S provides more certainty that your camera will focus exactly where you want.
Continuous servo can be useful for rapidly moving subjects such as flying birds. But, like autofocus tracking, I find that it is often overused by wildlife photographers. In my experience, AF-C often ends up racking focus too far and misfocusing when your subject is staying pretty still, getting stuck in an out-of-focus state. AF-S provides more certainty that your camera will focus exactly where you want.