I did a little thinking and a little looking around online, could be the following
-to much stress on the gpu ( heating and or not enough wattage depending on psu )
-different drivers seem to handle Bf3 differently from the latest to some older ones that may run the game better or smoother.
-what resolution you could be playing on
-your cpu seems to be a lower end quad core (back door) Meaning some fetures like hyperthreading are not included as well for Turbo Boost Technology. Higher end Quad cores have some access to these options, such as the i5 some are not, but there are more transistors and more threads, your quad has 4 and an (depending on model) the i7 would have 8 threads. Threads of the cpu let the application take full advantage to its processing power. What ever processor was used to take the benchmark could have been different most likely.
No system is going to be perfectly the same to one another.