Is Gracie jiu-jitsu really best for winning a fight, or just for the controlled environments in MMA-style competitions? I frequently hear Krav Maga cited as the most effective for real world fighting. Grappling with parties unknown seems dangerous.
Another thing to consider, is take a look at the all-around grappling skills of a top wrestler, judoka, bjj practitioner, etc. Do we really believe that their all-around skills wouldn't enable them to effectively use forbidden techniques such as ball punches or eye gouges or whatever? A skilled grappler is going to win a grappling contest, and a skilled striker will win a striking contest, regardless of the finishing techniques they employ.
I don't have specific experience with Krav per se, but the self-defense I learned getting my Karate BB was kravesque. Krav is fine, but I think of it a little like crossfit; it's mostly a marketing thing. In my estimation, krav can be great for self-defense. But anything where you focus on one or two practical defense moves is great for self-defense. Get good at one or two things and drill it 10,000 times.
With all the excitement and adrenaline, not only did every single student get 'stabbed' - many of them didn't notice until the exercise was over and the instructor pointed out the 'stab wounds'.
I'm not sure there's any amount of BJJ that would make me confident to grapple a guy who could have a concealed knife.