What FSB and CPU multi are using?
390*9 or close to?
If so, going with a 1:1 ratio will put you at 780Mhz RAM speed.
But you should be able to get 5-5-5-15 Timings.
Looks as if your RAM is Rated at
So this may be the best route.
Quickest way to compare is run a quick memory assesment. CMD Prompt and type : winsat mem
Youll get a general idea of the bandwidth.
TBH, there will likely be no noticeable real world difference.
Only in a benchmark.
But I also understand the desire to tweak and get the most you can
Try both settings and see what your system likes the best with the things you do the most often.
Every setup has a different "happy spot"