A signal mirror is useful for directing searchers to you, but is useless for telling them you have a problem. I actually have both a beacon and an inReach--I got the beacon when I started doing hikes that weren't part of a group, but were still on fairly popular trails. This year I've been deliberately avoiding the crowds so I added an inReach.
With the beacon they'll know exactly who and where you are (but nothing about the nature of the problem) and it also transmits a homing signal for aircraft. With the inReach if you just trip the SOS they only get who and where, but you also have text messaging so that you can communicate how urgent the situation is and what it will take to get you out. (Safe but unable to extract won't get anything like the response that femoral artery severed, tourniquet applied gets.)
With the beacon they'll know exactly who and where you are (but nothing about the nature of the problem) and it also transmits a homing signal for aircraft. With the inReach if you just trip the SOS they only get who and where, but you also have text messaging so that you can communicate how urgent the situation is and what it will take to get you out. (Safe but unable to extract won't get anything like the response that femoral artery severed, tourniquet applied gets.)