Vocal performance, whether singing or speech, is arguably one a microphone's most important uses. Clarity and articulation are vitally important -- a mic must be able to capture a voice's subtle nuances, as well as explosive peaks. Immunity to rough handling and high humidity are also critical to the mic's long term survival. A microphone's polar pattern should also be considered, as far as feedback rejection is concerned.
Some users prefer a condenser's extended high frequency response and ability to resolve delicate input signals, while others find dynamics to be more versatile, or warmer sounding. Many vocal mics have a flatter, more linear frequency response, while other mics offer a "tone" curve that boosts presence and low frequencies.