In general a dual processor will be faster than two computer doing network rendering. A dual processor is also faster than a dual core processor. Our tests show that you get almost a factor 2 on pure rendering with 2 processors and about a 60% increase with a dual core processor. This is true on Windows. On Mac Os X, dual processor systems do not perform as well mostly because the multithreading calls on the Mac are really slow at this point. You can still get a factor of 2 in some cases but most of the time it is only a 40 - 50 % speed up.