The only way I believe a computer could out-do a very skilled discretionary trader is with highly advanced artificial intelligence. The system would need to learn to trade much the way a human does. This kind of technology is still very far off... And well, to tell you the truth, it scares the crap out of me. BTW... It is easier to make bigger % profits on a smaller account simply because trading is 80% phychological. If tommorrow I started trading with an account size 5 times bigger than what I have now, I am pretty sure my performance would be altered. Its like war... In a controlled training exercise you may be the best soldier in your group, but that doesnt mean you would do as well in real combat. Fear and anxiety play a very strong role in performance.