I'm assuming you are talking about Intel systems. In games, you probably won't tell much at all between the two. It's the memory intensive apps that make the biggest differences. If you can run tight timings at 5:4 ratio, that's not really much different than 1:1 ratio if you have to use relaxed timings. Really, what helps performance the most is higher FSB. Choose whichever ratio gives you the highest stable overclock at the best timings.