As I understand it, this setting controls the preview the program creates on your timeline onlly. It has nothing to do with your actual output.
In other words, changing the setting will slightly improve the speed at which it renders but decreases the quality -- though I'd suspect it does neither to a significant degree. (You can do a comparison test if you'd like and report on your results.)
And, again, it does not affect your final output. So, if you've got a decently powered computer, I personally don't think it's worth changing the setting.