Should I use regular glasses or contact lenses if I have mild astigmatism?

Depends. If very mild, you can live with the slight distortion if you have no other refractive problems (myopia or hyperopia). Both glasses and contact lenses can correct astigmatism which is an ovalness of the eye corrected by a reverse oval in the glasses or contacts. Which to use is a personal choice. If needed only occasionally, glasses are the best. If you like the clarity all the time, try contac.