As Graham says, for SD material, you should use the new global setting and set the OSD value to Normal; also make sure you’ve whitelisted 480p and 576p resolutions.
As discussed in another thread, if the output resolution is higher than 576p and your video is 4:3 (for example, if you’re playing a 1440x1080 video) then the new global option will give you slightly-less-than-optimal output. For that, I’d suggest setting the global setting to Normal as well. But the rest of the time, go with what Graham tells you.
(I imagine that issue will be addressed at some point, and the new option for the global setting will then become the desirable default all the time).