There is a Queuing theory conclusion that one cpu at speed 2x is better than two cpus at speed x. The reason is that it takes overhead to schedule two and also each cpu can interfere with the other through locks, or memory access. But to reduce power consumption today, the trend is to 2 cpus at speed x. Increasing the speed causes a disproportionate increase in power consumption. The two cpu solution generally uses less power. What is the difference expected in performance? Frankly, it is hard to tell, In most cases, it will be ZERO and in other cases (with a lock wanted by cpu a which is held by cpu b ) it could be 1% to 2%. Over an hour, that 1% to 2% would wash out, meaning, you should FORGET ABOUT IT. Go for 2 cpu, shared cache on the die. (Intel or AMD)