Both microphones belong to different categories in the TG-series: the cardioid polar pattern of TG V50 has a larger frontal area, where it picks up sound from. You don´t need to use it exactly on axis, even two or three vocalists can use it at the same time. Via the larger area, it also picks up more stage wash.
The hypercardioid pattern of TG V70 is narrower in front of the mic, it has to be spoken or sang to exactly from the front but picks up less leakage from other instruments on stage.