Bro, Street Fights have changed with MMA.
Remember when people use to say "Fight like a man, stand up only" or "Only Girls Kick".
That shit doesn't fly anymore. A Street fight now is what people see on MMA.
So yes an actual Brawler who sees MMA and has been in certain MMA positions in real street fights>Boxer.
You gotta keep in mind that most street fights are not in the park...They take place in houses/stores/bars etc, close spaces where you cant run away...They will eventually Clinch and the fight WILL go to the ground.
A person who has seen MMA and experienced it in a street fight has some knowledge on passing the guard, getting full mount...hell they even know how to do a basic RNC....The boxer would be screwed.