Quite honestly, I can't tell a difference between Battery Saver modes. I run mine on Maximum battery saver...
If you're looking for performance though..well turn up the volume and run in performance. Truthfully though, I think there is more to the performace of the DX than just the setting for the battery. The battery setting is just to try and mitigate the quick drain. Still, you can kill it quickly by having the setting of your other apps, just 'how long you use the phone', and what you're asking the processor to deliver.
So, depending on what you're looking for - battery longevity or the speed of the DX...can make the difference in how you set up that part. Again, the overall setting pf the DX, plus it's apps and widgetry, and of course, how you use it, will determine the performance.