1) In the ring I would be fighting a trained fighter, in the street I am not. 2) The object of fighting is to win the match by scoring more points on the judges score card. In the street you win by creating the opportunity to escape. If I kick you in the bollocks and run away in the ring I get DQ'd, in the street if I kick you in the bollocks and run away I have achieved my objective. 3) in the street I can use brain engagement and pre-emptive striking, in the ring I cannot. 4) In the ring certain techniques and certain areas of the body are banned, in the street they are not. Like who? Geoff Thompson, ex bouncer and world renowned self protection expert only ever used two techniques, one punch and one kick. he states in his books that he has seen people on the floor "tearing the guy a new a**hole, only to get stabbed by his mates". In SD you need to learn how to get back to your feet as quickly as possible, BJJ does not teach you that, it teaches you to roll around on the floor looking for a heel hook or a triangle.