◆ Both are famous variable red giants/supergiants of spectral type M, but at very different evolutionary stages.
◆ Mira is a low-mass AGB star on its final evolutionary phase before becoming a planetary nebula; Betelgeuse is a massive red supergiant heading for a supernova.
◆ Mira has a pulsation period of ~332 days with an enormous magnitude range; Betelgeuse shows semi-regular variability.
◆ Betelgeuse is vastly larger at ~887 R☉ versus Mira's ~332 R☉.
◆ Mira has a remarkable 13-light-year tail of shed material trailing behind it through the interstellar medium.