As I recall, the Glock was not allowed in those tests. I think it was because it lacked a manual safety. I always thought that was a political decision.
I had an early Glock 17 and a 17L. Both of them jammed quite a bit and mine were not the only ones.
It was eventually traced to a series of bad magazines. You could identify them because you could see brass on the feed lips. Maybe it was the ones in which you could not see brass, I have actually forgotten.
They fixed the problem and I suspect Glocks are now as reliable as any.
I think it was because it was a foreign made gun. Beretta had a US factory.
http://www.berettadefence.com/index.aspx?m=53&did=144