Glove weight is the most commonly misunderstood part.
A boxing glove will absorb the initial impact so will ensure that the puncher's hand is less likely to be damaged, and also does a lot to protect to the face of the person being punched.
However, there's lot of research that highlights that instead of getting damage to the outside of the face, there can be significant damage to the inside of the head due to the more concussive type of impact that such gloves produce
MMA gloves are much lighter, they're likely to inflict more visible damage to the skin, but in a less concussive way.
That's before you consider that boxing is 12x3 minute rounds so totalling up to 36 minutes, whereas MMA is typically 3x5 or 5x5 minute rounds.
Also, a boxer's primary target is the head. 95% of the punches thrown will be aimed for the head.
In MMA it's a much lower percentage, with kicks to the body and legs as well as often significant periods of grappling with no strikes at all.
Both are combat sports with the potential to seriously hurt or injure someone, however, so is rugby.
There was a theory that a lot of the bad press about MMA used to come from boxing authorities and promoters who were concerned about a new sport impacting their profits.
The term cage fighting didn't really do MMA many favours either