The jump from 1200 to 1333 will not be very noticeable, especially if you get good tight timings as at that type of speed, the timings will probably make as much difference as the clock.
Edit- Especially since you will only be clocked at 1200, you can possibly even run the RAM at slightly tighter timings than they are rated for and get a little bit better performance out of it.
That is great to hear. Now, are timings edited in BIOS or via a program? I did hear someone else mention underclocking RAM could give you better timings.