[PCGH] Left 4 Dead 2: Unfair performance benefits with cut version?

The guys at PCGH discovered some weird things going on in Left 4 Dead 2 demo when comparing the uncut and the cut version. There is some performance difference up to 40 percent. PCGH claims that even if you have nice fps overall with the uncut version, in critical situations this might give players of the cut version unfair advantages.