From what I've read online, the 5x5 structure often leads to quicker stalling in progression for some than doing 3x5 like starting strength has you do for squat, overhead, and bench.
Also, some people really don't need to start as light as SL will have you starting on. Anecdotally, a friend of mine with an athletic background says when he starting weight training for college sports, he could bench over 200lbs for one rep having never seriously trained before. Starting with just the bar like SL recommends would be a big stall in his progress. On SL it'd take him about 53 weeks to bench 200 for 5x5 if starting with the bar and increasing by 2.5 pounds each bench exercise (1.5 times per week).
Also, Mehdi has no proper training in the background. Someone like Rippetoe, author of starting strength, has years of experience in powerlifting and coaching.
Quick article for further reading.
http://www.powerliftingtowin.com/stronglifts-5x5/
It mostly looks at SL from a powerlifting perspective, but much of the criticism is still valid.