Not sure what you think would be so different, getting taken down on concrete would simply hurt more.
Boxing has far less real-life-applicable rules than MMA, since a boxer in a street fight would require the other person to stay stood up and not do any kicks, wrestling, etc etc. Even street brawls go to the ground most of the time.
To point out Tyson would fight dirty and bite your nuts does nothing for your Boxing vs MMA argument, in fact it simply highlights how worthless Tyson's boxing ability would be if he fought say...Fedor or Brock or whoever.
Here's an shitty boxer/brawler vs a shitty sub-par MMA guy. 40 seconds in boxing guy is on his back and has no idea what's happening.